We wanted the first four factors, and so the way we got two is we said six minus four. Six minus four, that's going to get us what we want to get, that's going to give us the number that we want to get rid of. So we wanted to get rid of two, or the factors we want to get rid of. So that's going to give us two factorial. So if we use six minus four factorial, then that's going to give us two factorial, which is two times one, and then these cancel out, and we are all set. And so this is one way, this is, you know, I put in the particular numbers here, but this is a review of the permutations formula, where people say, hey, if I'm saying n, if I'm taking n things, and I want to figure out how many permutations are there of putting them into, let's say, k spots, it's going to be equal to n factorial over n minus k factorial. That's exactly what we did over here, where six is n, and k, or four, is k. Four is k. Actually, let me color code the whole thing so that we see the parallel.