Do you need to use iosbase hacks? scanf is fast enough without them.

If you use

ios_base::sync_with_stdio(false);

You should not use scanf/printf, cin/cout at the same time. Or you can submit code on Visual C++

cin and cout are synced to stdin and stdout by default, so that people can use both C I/O and C++ I/O at the same time. You disabled it with ios_base::sync_with_stdio(false), so there are now two separate buffers which messes things up. This is why you don't write code which you don't understand. ios_base::sync_with_stdio(false) disables syncing between cin/cout and scanf/printf, and cin.tie(nullptr) disables cout being flushed automatically when you do stuff with cin. They're not magic lines of code that speeds everything up.