foo.cc: In function 'int main()':
foo.cc:6:2: error: 'cin' was not declared in this scope
  cin>>x;
  ^~~
foo.cc:6:2: note: suggested alternative: 'main'
  cin>>x;
  ^~~
  main
foo.cc:9:3: error: 'cout' was not declared in this scope
   cout<<x+y<<endl;
   ^~~~
foo.cc:9:14: error: 'endl' was not declared in this scope
   cout<<x+y<<endl;
              ^~~~
foo.cc:9:14: note: suggested alternative: 'enum'
   cout<<x+y<<endl;
              ^~~~
              enum