/in/foo.cc: In function 'int main()':
/in/foo.cc:6:2: error: 'cin' was not declared in this scope
  cin >>a>>b;
  ^~~
/in/foo.cc:7:2: error: 'cout' was not declared in this scope
  cout <<a+b<< endl ;
  ^~~~
/in/foo.cc:7:15: error: 'endl' was not declared in this scope
  cout <<a+b<< endl ;
               ^~~~