The number of ways to arrange three things in three spots, it's three factorial. So we could just divide this. We could just divide this by K factorial, and so this would get us, this would get us N factorial divided by K factorial, K factorial times, times N minus K factorial. N minus K, N minus K, and I'll put the factorial right over there. And this right over here is the formula, this right over here is the formula for combinations. Sometimes this is also called the binomial coefficient. Some people will call this N choose K. They'll also write it like this.