/in/foo.cc: In function 'int main()':
/in/foo.cc:7:18: error: 'scanf_s' was not declared in this scope
  scanf_s("%d", &n);
                  ^
/in/foo.cc:6:17: warning: unused variable 'mid' [-Wunused-variable]
  int n, a[101], mid, all=0, ans=0;
                 ^~~