Could you explain to me (s.length / 2 - 1) ? To me it is saying find the middle and move the index down one in case it is an even number string length so you can return both numbers. I don't get it, I do understand the deprication of substr and I used substring in my solution. Or if you could maybe explain what the (s.lenght / 2) - 1 means that will help as well.