So what is the number of ways, number of ways to arrange K things, K things in K spots? And I encourage you to pause the video, because this is actually a review from the first permutation video. Well, if you have K spots, let me do it. So this is the first spot, the second spot, third spot, and then you're going to go all the way to the Kth spot. Well, for the first spot, there could be K possibilities. There's K things that could take the first spot. Now, for each of those K possibilities, how many things could be in the second spot?