/in/foo.c: In function 'main':
/in/foo.c:5:4: error: 'cin' undeclared (first use in this function)
    cin>>a>>b;
    ^~~
/in/foo.c:5:4: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:6:2: error: 'cout' undeclared (first use in this function)
  cout<<a+b;
  ^~~~