/in/foo.cc: In function 'int main()':
/in/foo.cc:5:9: error: 'cin' was not declared in this scope
    5 |         cin>>123 456 789;
      |         ^~~
/in/foo.cc:6:9: error: 'cout' was not declared in this scope
    6 |         cout<<456<<endl;
      |         ^~~~
/in/foo.cc:6:20: error: 'endl' was not declared in this scope
    6 |         cout<<456<<endl;
      |                    ^~~~