Language: C++


        cin >> field[i];
    }

    int S = n * m, T = n * m + 1;
    atcoder::mf_graph<int> mf(n*m+2);
    
    for(int i = 0;i < n;i++){
        for(int j = 0;j < m;j++){
            if(i && field[i][j] == '.' && field[i-1][j] == '.'){
                if((i + j) % 2){
                    mf.add_edge(i * m + j, (i-1) * m + j, 1);
                }
                else{
                    mf.add_edge((i-1) * m + j, i * m + j, 1);
                }
            }
            if(j && field[i][j] == '.' && field[i][j-1] == '.'){
                if((i + j) % 2){
                    mf.add_edge(i * m + j, i * m + j - 1, 1);
                }
                else{
                    mf.add_edge(i * m + j - 1, i * m + j, 1);
                }
            }
            if((i + j) % 2){
                mf.add_edge(S, i * m + j, 1);
            }
            else{
                mf.add_edge(i * m + j, T, 1);
            }
        }
    }
    int mx = mf.flow(S, T);
    for(auto e: mf.edges()){
        if(e.from != S && e.to != T && e.flow == 1){
            int fi = e.from / m, fj = e.from % m;
            int ti = e.to / m, tj = e.to % m;
            if(fi == ti){
                field[fi][min(fj, tj)] = '>';
                field[fi][max(fj, tj)] = '<';
            }
            else{
                field[min(fi, ti)][fj] = 'v';
                field[max(fi, ti)][fj] = '^';
            }
        }
    }
    cout << mx << endl;
    for(int i = 0;i < n;i++)cout << field[i] << endl;
    return 0;
}

Compiler output:
a.cc:2:9: error: 'cin' does not name a type
    2 |         cin >> field[i];
      |         ^~~
a.cc:3:5: error: expected declaration before '}' token
    3 |     }
      |     ^
a.cc:5:13: error: 'n' was not declared in this scope
    5 |     int S = n * m, T = n * m + 1;
      |             ^
a.cc:5:17: error: 'm' was not declared in this scope
    5 |     int S = n * m, T = n * m + 1;
      |                 ^
a.cc:6:5: error: 'atcoder' does not name a type
    6 |     atcoder::mf_graph<int> mf(n*m+2);
      |     ^~~~~~~
a.cc:8:5: error: expected unqualified-id before 'for'
    8 |     for(int i = 0;i < n;i++){
      |     ^~~
a.cc:8:19: error: 'i' does not name a type
    8 |     for(int i = 0;i < n;i++){
      |                   ^
a.cc:8:25: error: 'i' does not name a type
    8 |     for(int i = 0;i < n;i++){
      |                         ^
a.cc:34:14: error: 'mf' was not declared in this scope; did you mean 'mx'?
   34 |     int mx = mf.flow(S, T);
      |              ^~
      |              mx
a.cc:34:25: error: 'T' was not declared in this scope
   34 |     int mx = mf.flow(S, T);
      |                         ^
a.cc:35:5: error: expected unqualified-id before 'for'
   35 |     for(auto e: mf.edges()){
      |     ^~~
a.cc:49:5: error: 'cout' does not name a type
   49 |     cout << mx << endl;
      |     ^~~~
a.cc:50:5: error: expected unqualified-id before 'for'
   50 |     for(int i = 0;i < n;i++)cout << field[i] << endl;
      |     ^~~
a.cc:50:19: error: 'i' does not name a type
   50 |     for(int i = 0;i < n;i++)cout << field[i] << endl;
      |                   ^
a.cc:50:25: error: 'i' does not name a type
   50 |     for(int i = 0;i < n;i++)cout << field[i] << endl;
      |                         ^
a.cc:51:5: error: expected unqualified-id before 'return'
   51 |     return 0;
      |     ^~~~~~
a.cc:52:1: error: expected declaration before '}' token
   52 | }
      | ^