mirror of
https://github.com/aicodix/modem.git
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added LDPC forward error correction
This commit is contained in:
Ahmet Inan
parent
1e0b2199af
commit
7ba95fb000
4 changed files with 182 additions and 25 deletions
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@ -3,10 +3,10 @@
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Quick start:
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Create file ```uncoded.dat``` with ```64576``` bits of random data:
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Create file ```uncoded.dat``` with ```42976``` bits of random data:
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```
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dd if=/dev/urandom of=uncoded.dat bs=1 count=8072
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dd if=/dev/urandom of=uncoded.dat bs=1 count=5372
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```
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Encode file ```uncoded.dat``` to ```encoded.wav``` [WAV](https://en.wikipedia.org/wiki/WAV) audio file with 8000 Hz sample rate, 16 bits and only 1 (real) channel:
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28
decode.cc
28
decode.cc
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@ -4,6 +4,7 @@ OFDM modem decoder
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Copyright 2021 Ahmet Inan <inan@aicodix.de>
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*/
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#include <algorithm>
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#include <iostream>
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#include <cassert>
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#include <cmath>
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@ -25,6 +26,8 @@ namespace DSP { using std::abs; using std::min; using std::cos; using std::sin;
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#include "crc.hh"
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#include "osd.hh"
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#include "psk.hh"
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#include "ldpc_tables.hh"
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#include "ldpc_decoder.hh"
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#include "galois_field.hh"
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#include "bose_chaudhuri_hocquenghem_decoder.hh"
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@ -152,12 +155,12 @@ template <typename value, typename cmplx, int rate>
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struct Decoder
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{
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typedef DSP::Const<value> Const;
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typedef PhaseShiftKeying<8, cmplx, value> Mod;
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typedef PhaseShiftKeying<8, cmplx, int8_t> Mod;
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static const int symbol_len = (1280 * rate) / 8000;
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static const int filter_len = (((21 * rate) / 8000) & ~3) | 1;
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static const int guard_len = symbol_len / 8;
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static const int code_bits = 64800;
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static const int data_bits = code_bits - 32 - 12 * 16;
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static const int data_bits = code_bits - 32 - 12 * 16 - 21600;
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static const int code_cols = 432;
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static const int code_rows = code_bits / code_cols / Mod::BITS;
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static const int code_off = -216;
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@ -183,7 +186,9 @@ struct Decoder
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GF gf;
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CODE::BoseChaudhuriHocquenghemDecoder<24, 1, 65343, GF> bchdec1;
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CODE::OrderedStatisticsDecoder<255, 71, 4> osddec;
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CODE::LDPCDecoder<DVB_T2_TABLE_A3, 1> ldpcdec;
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int8_t genmat[255*71];
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int8_t code[code_bits];
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cmplx head[symbol_len], tail[symbol_len];
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cmplx fdom[symbol_len], tdom[buffer_len], resam[buffer_len];
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value phase[symbol_len/2];
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@ -331,21 +336,22 @@ struct Decoder
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for (int i = 0; i < buffer_len; ++i)
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tdom[i] = resam[i] * osc();
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value precision = 16;
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cmplx *cur = tdom + symbol_pos - (code_rows + 1) * (symbol_len + guard_len);
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fwd(fdom, cur);
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for (int j = 0; j < code_rows; ++j) {
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for (int i = 0; i < code_cols; ++i)
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head[bin(i+code_off)] = fdom[bin(i+code_off)];
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fwd(fdom, cur += symbol_len+guard_len);
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for (int i = 0; i < code_cols; ++i) {
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value tmp[Mod::BITS];
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Mod::hard(tmp, fdom[bin(i+code_off)] / head[bin(i+code_off)]);
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for (int k = 0; k < Mod::BITS; ++k) {
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int l = Mod::BITS * (code_cols * j + i) + k;
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CODE::set_le_bit(out, l, tmp[k] < 0);
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}
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}
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for (int i = 0; i < code_cols; ++i)
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Mod::soft(code+Mod::BITS*(code_cols*j+i), fdom[bin(i+code_off)]/head[bin(i+code_off)], precision);
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}
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int count = ldpcdec(code, code+data_bits+32+12*16);
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if (count < 0)
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std::cerr << "payload LDPC decoding did not converge." << std::endl;
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for (int i = 0; i < data_bits+32+12*16; ++i)
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CODE::set_le_bit(out, i, code[i] < 0);
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int ret = bchdec1(out, out+(data_bits+32)/8, 0, 0, data_bits+32);
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if (ret < 0) {
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std::cerr << "payload BCH error." << std::endl;
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@ -411,7 +417,7 @@ int main(int argc, char **argv)
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std::cerr << "Couldn't open file \"" << output_name << "\" for writing." << std::endl;
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return 1;
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}
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const int data_len = code_len - (32 + 12 * 16) / 8;
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const int data_len = code_len - (32 + 12 * 16 + 21600) / 8;
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for (int i = 0; i < data_len; ++i)
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output_file.put(output_data[i]);
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delete []output_data;
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25
encode.cc
25
encode.cc
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@ -17,17 +17,19 @@ Copyright 2021 Ahmet Inan <inan@aicodix.de>
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#include "mls.hh"
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#include "crc.hh"
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#include "psk.hh"
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#include "ldpc_tables.hh"
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#include "ldpc_encoder.hh"
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#include "galois_field.hh"
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#include "bose_chaudhuri_hocquenghem_encoder.hh"
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template <typename value, typename cmplx, int rate>
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struct Encoder
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{
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typedef PhaseShiftKeying<8, cmplx, value> Mod;
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typedef PhaseShiftKeying<8, cmplx, int8_t> Mod;
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static const int symbol_len = (1280 * rate) / 8000;
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static const int guard_len = symbol_len / 8;
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static const int code_bits = 64800;
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static const int data_bits = code_bits - 32 - 12 * 16;
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static const int data_bits = code_bits - 32 - 12 * 16 - 21600;
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static const int code_cols = 432;
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static const int code_rows = code_bits / code_cols / Mod::BITS;
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static const int mls0_len = 127;
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@ -41,6 +43,8 @@ struct Encoder
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CODE::CRC<uint32_t> crc1;
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CODE::BoseChaudhuriHocquenghemEncoder<255, 71> bchenc0;
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CODE::BoseChaudhuriHocquenghemEncoder<65535, 65343> bchenc1;
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CODE::LDPCEncoder<DVB_T2_TABLE_A3> ldpcenc;
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int8_t code[code_bits];
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cmplx fdom[symbol_len];
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cmplx tdom[symbol_len];
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cmplx guard[guard_len];
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@ -87,7 +91,7 @@ struct Encoder
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for (int i = 0; i < symbol_len; ++i)
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fdom[i] = 0;
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for (int i = code_off; i < code_off + code_cols; ++i) {
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value tmp[Mod::BITS];
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int8_t tmp[Mod::BITS];
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for (int k = 0; k < Mod::BITS; ++k)
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tmp[k] = 1 - 2 * seq2();
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fdom[bin(i)] = code_fac * Mod::map(tmp);
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@ -159,15 +163,12 @@ struct Encoder
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for (int i = 0; i < 4; ++i)
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inp[data_bits/8+i] = (crc1() >> (8*i)) & 255;
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bchenc1(inp, inp+(data_bits+32)/8, data_bits+32);
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for (int i = 0; i < data_bits+32+12*16; ++i)
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code[i] = 1 - 2 * CODE::get_le_bit(inp, i);
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ldpcenc(code, code+data_bits+32+12*16);
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for (int j = 0; j < code_rows; ++j) {
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for (int i = 0; i < code_cols; ++i) {
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value tmp[Mod::BITS];
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for (int k = 0; k < Mod::BITS; ++k) {
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int l = Mod::BITS * (code_cols * j + i) + k;
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tmp[k] = 1 - 2 * CODE::get_le_bit(inp, l);
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}
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fdom[bin(i+code_off)] *= Mod::map(tmp);
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}
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for (int i = 0; i < code_cols; ++i)
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fdom[bin(i+code_off)] *= Mod::map(code+Mod::BITS*(code_cols*j+i));
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symbol();
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}
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schmidl_cox();
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@ -239,7 +240,7 @@ int main(int argc, char **argv)
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return 1;
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}
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const int code_len = 64800 / 8;
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const int data_len = code_len - (32 + 12 * 16) / 8;
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const int data_len = code_len - (32 + 12 * 16 + 21600) / 8;
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uint8_t *input_data = new uint8_t[code_len];
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for (int i = 0; i < data_len; ++i)
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input_data[i] = input_file.get();
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150
ldpc_tables.hh
Normal file
150
ldpc_tables.hh
Normal file
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@ -0,0 +1,150 @@
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/*
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LDPC tables
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Table entries below copied from:
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https://www.etsi.org/deliver/etsi_en/302700_302799/302755/01.04.01_60/en_302755v010401p.pdf
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Copyright 2018 Ahmet Inan <inan@aicodix.de>
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*/
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#pragma once
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struct DVB_T2_TABLE_A3
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{
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static const int M = 360;
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static const int N = 64800;
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static const int K = 43200;
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static const int LINKS_MIN_CN = 9;
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static const int LINKS_MAX_CN = 10;
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static const int LINKS_TOTAL = 215999;
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static const int DEG_MAX = 13;
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static constexpr int DEG[] = {
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13, 3, 0
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};
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static constexpr int LEN[] = {
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12, 108, 0
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};
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static constexpr int POS[] = {
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317, 2255, 2324, 2723, 3538, 3576, 6194, 6700, 9101, 10057, 12739, 17407, 21039,
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1958, 2007, 3294, 4394, 12762, 14505, 14593, 14692, 16522, 17737, 19245, 21272, 21379,
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127, 860, 5001, 5633, 8644, 9282, 12690, 14644, 17553, 19511, 19681, 20954, 21002,
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2514, 2822, 5781, 6297, 8063, 9469, 9551, 11407, 11837, 12985, 15710, 20236, 20393,
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1565, 3106, 4659, 4926, 6495, 6872, 7343, 8720, 15785, 16434, 16727, 19884, 21325,
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706, 3220, 8568, 10896, 12486, 13663, 16398, 16599, 19475, 19781, 20625, 20961, 21335,
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4257, 10449, 12406, 14561, 16049, 16522, 17214, 18029, 18033, 18802, 19062, 19526, 20748,
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412, 433, 558, 2614, 2978, 4157, 6584, 9320, 11683, 11819, 13024, 14486, 16860,
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777, 5906, 7403, 8550, 8717, 8770, 11436, 12846, 13629, 14755, 15688, 16392, 16419,
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4093, 5045, 6037, 7248, 8633, 9771, 10260, 10809, 11326, 12072, 17516, 19344, 19938,
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2120, 2648, 3155, 3852, 6888, 12258, 14821, 15359, 16378, 16437, 17791, 20614, 21025,
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1085, 2434, 5816, 7151, 8050, 9422, 10884, 12728, 15353, 17733, 18140, 18729, 20920,
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856, 1690, 12787,
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6532, 7357, 9151,
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4210, 16615, 18152,
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11494, 14036, 17470,
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2474, 10291, 10323,
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1778, 6973, 10739,
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4347, 9570, 18748,
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2189, 11942, 20666,
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3868, 7526, 17706,
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8780, 14796, 18268,
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160, 16232, 17399,
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1285, 2003, 18922,
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4658, 17331, 20361,
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2765, 4862, 5875,
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4565, 5521, 8759,
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3484, 7305, 15829,
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5024, 17730, 17879,
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7031, 12346, 15024,
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179, 6365, 11352,
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2490, 3143, 5098,
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2643, 3101, 21259,
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4315, 4724, 13130,
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594, 17365, 18322,
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5983, 8597, 9627,
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10837, 15102, 20876,
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10448, 20418, 21478,
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3848, 12029, 15228,
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708, 5652, 13146,
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5998, 7534, 16117,
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2098, 13201, 18317,
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9186, 14548, 17776,
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5246, 10398, 18597,
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3083, 4944, 21021,
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13726, 18495, 19921,
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6736, 10811, 17545,
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10084, 12411, 14432,
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1064, 13555, 17033,
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679, 9878, 13547,
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3422, 9910, 20194,
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3640, 3701, 10046,
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5862, 10134, 11498,
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5923, 9580, 15060,
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1073, 3012, 16427,
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5527, 20113, 20883,
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7058, 12924, 15151,
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9764, 12230, 17375,
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772, 7711, 12723,
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555, 13816, 15376,
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10574, 11268, 17932,
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15442, 17266, 20482,
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390, 3371, 8781,
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10512, 12216, 17180,
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4309, 14068, 15783,
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3971, 11673, 20009,
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9259, 14270, 17199,
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2947, 5852, 20101,
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3965, 9722, 15363,
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1429, 5689, 16771,
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6101, 6849, 12781,
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3676, 9347, 18761,
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350, 11659, 18342,
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5961, 14803, 16123,
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2113, 9163, 13443,
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2155, 9808, 12885,
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2861, 7988, 11031,
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7309, 9220, 20745,
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6834, 8742, 11977,
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2133, 12908, 14704,
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10170, 13809, 18153,
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13464, 14787, 14975,
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799, 1107, 3789,
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3571, 8176, 10165,
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5433, 13446, 15481,
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3351, 6767, 12840,
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8950, 8974, 11650,
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1430, 4250, 21332,
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6283, 10628, 15050,
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8632, 14404, 16916,
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6509, 10702, 16278,
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15900, 16395, 17995,
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8031, 18420, 19733,
|
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3747, 4634, 17087,
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4453, 6297, 16262,
|
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2792, 3513, 17031,
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14846, 20893, 21563,
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17220, 20436, 21337,
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275, 4107, 10497,
|
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3536, 7520, 10027,
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14089, 14943, 19455,
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1965, 3931, 21104,
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2439, 11565, 17932,
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154, 15279, 21414,
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10017, 11269, 16546,
|
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7169, 10161, 16928,
|
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10284, 16791, 20655,
|
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36, 3175, 8475,
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2605, 16269, 19290,
|
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8947, 9178, 15420,
|
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5687, 9156, 12408,
|
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8096, 9738, 14711,
|
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4935, 8093, 19266,
|
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2667, 10062, 15972,
|
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6389, 11318, 14417,
|
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8800, 18137, 18434,
|
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5824, 5927, 15314,
|
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6056, 13168, 15179,
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3284, 13138, 18919,
|
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13115, 17259, 17332,
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};
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};
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