And so the probability of two unsuccessful trials is one minus P squared. And then one successful trial, just like that. So you get the general idea. So if I wanted to rewrite this, I'm just going to rewrite it to make it a little bit simpler. So the expected, at least for the purposes of this proof, so the expected value of X is equal to, I'll write this as one P plus two P times one minus P plus three P times one minus P squared. And we're going to keep going on and on and on forever like that. So how do we figure out this sum?