/in/foo.cc: In function 'int main()':
/in/foo.cc:5:5: error: 'cin' was not declared in this scope
     cin >> n;
     ^~~
/in/foo.cc:5:12: error: 'n' was not declared in this scope
     cin >> n;
            ^
/in/foo.cc:6:9: error: 'm' was not declared in this scope
  cin >> m;
         ^
/in/foo.cc:7:2: error: 'cout' was not declared in this scope
  cout << n << m;
  ^~~~