/in/foo.cc: In function 'int main()':
/in/foo.cc:7:5: error: 'cin' was not declared in this scope
     cin >> a >> b;
     ^~~
/in/foo.cc:8:5: error: 'cout' was not declared in this scope
     cout << a + b << endl;
     ^~~~
/in/foo.cc:8:22: error: 'endl' was not declared in this scope
     cout << a + b << endl;
                      ^~~~