Tails, heads, and tails. And we know already what the probability of each of these things are. There are 16 possible events. And each of these are one of those 16 possible events. So this is going to be 1 over 16. And so we're really saying the probability of getting exactly 1 heads is the same thing as the probability of getting heads in the first flip or the probability of getting heads in the first flip or heads in the second flip or heads in the third flip or heads in the fourth flip. And we can add the probabilities of these different things because they are mutually exclusive.