/in/foo.cc: In function 'int main()':
/in/foo.cc:23:18: error: 'scanf_s' was not declared in this scope
  scanf_s("%d", &n);
                  ^
/in/foo.cc:27:24: error: 'printf_s' was not declared in this scope
  printf_s("%lld\n", ans);
                        ^