For those of you who haven't, an integral is just the area under a curve, and you can watch the calculus videos if you want to learn a little bit more about how to do them. And this also applies to the discrete probability distributions. Let me draw one. The sum of all of the probabilities have to be equal to 1. In that example with the dice, or let's say, since it's faster to draw the coin, the two probabilities have to be equal to 1. So if this is 1, 0, where x is equal to 1 if we're heads, or 0 if we're tails, each of these have to be 0.5. Or they don't have to be 0.5, but if 1 was 0.6, the other one would have to be 0.4.