Once again, and this takes, I remember the first time I learned it, it took my brain a little while, so if it's taking a little while to think about it, not a big deal. It can be confusing at first, but it'll hopefully, if you keep thinking about it, hopefully you will see clarity at some moment. But what we want to do is we want to divide by all of the ways that you could arrange four things, because once again, in the permutations, it's counting all of the different arrangements of four things, but we don't want to count all of those different arrangements of four things. We want to just say, well, they're all one combination. So we want to divide by the number of ways to arrange four things, or the number of ways to arrange K things. So let me write this down. So what is the number of ways, number of ways to arrange K things, K things in K spots?