/in/foo.c: In function 'main':
/in/foo.c:5:5: error: 'cin' undeclared (first use in this function)
     cin >> n;
     ^~~
/in/foo.c:5:5: note: each undeclared identifier is reported only once for each function it appears in
/in/foo.c:5:12: error: 'n' undeclared (first use in this function)
     cin >> n;
            ^