/in/foo.cc: In function 'int main()':
/in/foo.cc:7:5: error: 'cin' was not declared in this scope
     cin >> n >> x;
     ^~~
/in/foo.cc:20:5: error: 'cout' was not declared in this scope
     cout << ans << endl;
     ^~~~
/in/foo.cc:20:20: error: 'endl' was not declared in this scope
     cout << ans << endl;
                    ^~~~