/in/foo.c: In function 'main':
/in/foo.c:10:16: warning: format '%lld' expects argument of type 'long long int', but argument 2 has type 'int' [-Wformat=]
     printf("%lld\n", ans);
                ^
/in/foo.c:7:5: warning: 'n' is used uninitialized in this function [-Wuninitialized]
     for (int i = 1; i <= n; ++i) {
     ^~~