What is the actual result type of std::chrono::duration::count function

What is the actual result type of std::chrono::duration::count function like in the following case:

std::chrono::duration_cast<std::chrono::milliseconds>(end - begin).count();

It seems like it is some rep type but what is it actually? I need to know the exact type to pass it to some other languages. Can I just cast it to long long, for example?