So there's a total of 10 steps, so 10 factorial. That's kind of the number of trials I have. Of that, I'm choosing 0 to go left. So 0 factorial divided by 10 minus 0 factorial, right? This is 10 choose 0. I'm choosing 0 left steps of the total 10 steps I'm taking times the probability of 0 left steps. 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.