And to appreciate the power of this, let's extend our example. Let's say that we have five seats, one, two, three, four, five, and we have five people, person A, B, C, D, and E. How many different ways can these five people sit in these five seats? Pause this video and figure it out. Well, you might immediately say, well, that's going to be five factorial which is going to be equal to five times four times three times two times one. Five times four is 20. 20 times three is 60. And then 60 times two is 120.