/in/foo.c: In function 'main':
/in/foo.c:6:8: error: 'cin' undeclared (first use in this function)
    6 |  while(cin >> n){
      |        ^~~
/in/foo.c:6:8: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:7:3: error: 'cout' undeclared (first use in this function)
    7 |   cout << n*n << endl;
      |   ^~~~
/in/foo.c:7:18: error: 'endl' undeclared (first use in this function)
    7 |   cout << n*n << endl;
      |                  ^~~~
/in/foo.c:8:1: error: expected declaration or statement at end of input
    8 | }
      | ^