/in/foo.cc: In function 'int main()':
/in/foo.cc:3:2: error: 'cin' was not declared in this scope
  cin >>a>>b;
  ^~~
/in/foo.cc:5:2: error: 'cout' was not declared in this scope
  cout << x << endl;
  ^~~~
/in/foo.cc:5:15: error: 'endl' was not declared in this scope
  cout << x << endl;
               ^~~~