But this one's even faster in a lot of ways, because you don't really have to even calculate the mean ahead of time. You can just say, OK, for each xi, I just perform this operation, and then I divide by n squared or n accordingly, and I'll also get to the variance. So you don't have to do this calculation before you figure out the whole variance. But anyway, I thought it would be instructive and hopefully give you a little bit more intuition behind the algebra dealing with sigma notation, if we kind of worked out these other ways to write variances. And frankly, some books will just kind of say, oh yeah, you know what, the variance could be written like this, or, and we're talking about the variance of a population, or it could be written like this, or maybe they'll even write it like this. And it's good to know that you can just do a little bit of simple algebraic manipulation and get from one to the other. Anyway, I've run out of time.