So it's the probability of a left step, I'm only taking 0 of them, times the probability of a right step, and I'm taking 10 of those. So that's where this number came from, this 0.001. That's what the binomial distribution tells us. And then this one, similarly, is 10 factorial over 1 factorial over 10 minus 1 factorial, and that's how I get that one. And once again, if you click on the actual cell, you'll see that explained. So we've done this multiple times, it's just the binomial calculation. And then right here, after this line right here, you can almost ignore it.