foo.cc: In function ‘bool check(int, int, int, int)’:
foo.cc:7:51: error: expected ‘]’ before ‘;’ token
    7 |                 for(int j=ya;j<=yb;j++)a[w[i][j]++;
      |                                                   ^
      |                                                   ]
foo.cc: In function ‘int main()’:
foo.cc:11:36: error: expected ‘;’ before ‘int’
   11 |         ios::sync_with_stdio(false)
      |                                    ^
      |                                    ;
   12 |         int n,m,ans=0;
      |         ~~~                         
foo.cc:13:14: error: ‘n’ was not declared in this scope; did you mean ‘yn’?
   13 |         cin>>n>>m;
      |              ^
      |              yn
foo.cc:13:17: error: ‘m’ was not declared in this scope
   13 |         cin>>n>>m;
      |                 ^
foo.cc:24:49: error: ‘ans’ was not declared in this scope; did you mean ‘abs’?
   24 |                                                 ans=max(ans,(ii-i+1)*(jj-j+1));
      |                                                 ^~~
      |                                                 abs
foo.cc:25:15: error: ‘ans’ was not declared in this scope; did you mean ‘abs’?
   25 |         cout<<ans;
      |               ^~~
      |               abs