/in/foo.cc: In function 'void dfs(int, int)':
/in/foo.cc:12:12: error: 'n' was not declared in this scope
  if(x<0||x>n||y<0||y>m)return ;
            ^
/in/foo.cc:12:22: error: 'm' was not declared in this scope
  if(x<0||x>n||y<0||y>m)return ;
                      ^
/in/foo.cc:20:37: error: 'max' was not declared in this scope
    f[tx][ty]=max(f[tx][ty],f[x][y]+1):
                                     ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:42:21: error: 'j' was not declared in this scope
    ans=max(ans,f[i][j]);
                     ^
/in/foo.cc:42:23: error: 'max' was not declared in this scope
    ans=max(ans,f[i][j]);
                       ^