/in/foo.cc: In function 'int main()':
/in/foo.cc:7:2: error: 'cin' was not declared in this scope
  cin >> a >> b;
  ^~~
/in/foo.cc:8:2: error: 'cout' was not declared in this scope
  cout << a+b << endl;
  ^~~~
/in/foo.cc:8:17: error: 'endl' was not declared in this scope
  cout << a+b << endl;
                 ^~~~