#include<bits/stdc++.h>
using namespace std;
void send_message(vector<bool>M,vector<bool>C){
  int pos=0;
  vector<bool>cs;
  for(int i=0;i<66;++i){
    cs.clear();
    for(int j=0;j<31;++j){
      if(C[j]||pos>=M.size()){cs.push_back(0);continue;}
      int k=0;
      for(;k<31;++k){
        if(!C[(j+k+1)%31])break;
      }
      if(i<k)cs.push_back(0);
      if(i==k)cs.push_back(1);
      cs.push_back(M[pos]);++pos;
    }
    send_packet(cs);
    if(pos>=M.size())return;
  }
}
vector<bool>receive_message(vector<vector<bool>>R){
  int dep[31],nxt[31];
  for(int i=0;i<31;++i)dep[i]=0,nxt[i]=0;
  for(int i=0;i<R.size();++i){
    for(int j=0;j<R[i].size();++j){
      if(nxt[j])continue;
      if(R[i][j]==1){
        nxt[j]=i+1;
      }
    }
  }
  bool tru[31];
  for(int i=0;i<31;++i)tru[i]=0;
  for(int i=0;i<31;++i){
    if(!dep[i]){
      int x=i;
      bool ok=0;
      while(1){
        if(dep[x+nxt[x]]){
          if(dep[(x+nxt[x])%31]+15==dep[x]){
            ok=1;break;
          }
        }
        dep[(x+nxt[x])%31]=dep[x]+1;
        x=(x+nxt[x])%31;
      }
      if(ok){
        for(int i=0;i<16;++i){
          tru[x]=1;x=(x+nxt[x])%31;
        }
      }
    }
  }
  vector<bool>cs={};
  for(int i=0;i<R.size();++i){
    for(int j=0;j<R[i].size();++j){
      if(!tru[j])continue;
      if(i>=nxt[j])cs.push_back(R[i][j]);
    }
  }
  return cs;
}

answer.code: In function ‘void send_message(std::vector<bool>, std::vector<bool>)’:
answer.code:18:5: error: ‘send_packet’ was not declared in this scope
   18 |     send_packet(cs);
      |     ^~~~~~~~~~~
stub.cpp: In function ‘int {anonymous}::sz(const C&)’:
stub.cpp:27:52: error: ‘size’ is not a member of ‘std’; did you mean ‘size_t’?
   27 | template<class C> int sz(const C& c) { return std::size(c); }
      |                                                    ^~~~
      |                                                    size_t
stub.cpp: In function ‘void {anonymous}::write_int_array(const int*, int)’:
stub.cpp:70:13: warning: init-statement in selection statements only available with ‘-std=c++17’ or ‘-std=gnu++17’
   70 |         if (int ret = fwrite(arr, sizeof(int), len, fout); len != ret) {
      |             ^~~
stub.cpp: In function ‘void {anonymous}::read_int_array(int*, int)’:
stub.cpp:105:13: warning: init-statement in selection statements only available with ‘-std=c++17’ or ‘-std=gnu++17’
  105 |         if (int ret = fread(arr, sizeof(int), len, fin); len != ret) {
      |             ^~~