And that's all of the other possibilities. And this is the only other leftover possibility. If you add them together, you're going to get one. Let me write it this way. The probability of not all tails plus the probability of all tails, well, this is essentially exhaustive. This is all of the possible circumstances. So your chances of getting either not all tails or all tails, and these are mutual exclusives, so we can add them, so the probability of not all tails or the probability of all tails is going to be equal to 1.