/in/foo.c: In function 'main':
/in/foo.c:6:5: error: 'cin' undeclared (first use in this function)
    6 |     cin >> n;
      |     ^~~
/in/foo.c:6:5: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:9:9: error: 'cout' undeclared (first use in this function)
    9 |         cout << 1;
      |         ^~~~
/in/foo.c:24:13: error: 'endl' undeclared (first use in this function)
   24 |     cout << endl;
      |             ^~~~