/in/foo.c: In function 'main':
/in/foo.c:6:9: error: 'cin' undeclared (first use in this function)
    6 |         cin>>a;
      |         ^~~
/in/foo.c:6:9: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:8:17: error: 'cout' undeclared (first use in this function)
    8 |                 cout<<"YES";
      |                 ^~~~