foo.cc: In function 'int main()':
foo.cc:6:2: error: 'cin' was not declared in this scope
  cin>>a>>b;
  ^~~
foo.cc:6:2: note: suggested alternative: 'main'
  cin>>a>>b;
  ^~~
  main
foo.cc:7:2: error: 'cout' was not declared in this scope
  cout<<a+b<<endl;
  ^~~~
foo.cc:7:13: error: 'endl' was not declared in this scope
  cout<<a+b<<endl;
             ^~~~
foo.cc:7:13: note: suggested alternative: 'enum'
  cout<<a+b<<endl;
             ^~~~
             enum