But I agree with this definition. So I want to get f of x within 0.5 of L. So this right over here would be L plus 0.5. And this right over here is L minus 0.5. And then you say, fine, I'm going to give you a range around c that if you take any x within that range, your f of x is always going to fall in this range that you care about. And so you look at this. And obviously, we haven't explicitly defined this function. But you can even eyeball it the way this function is defined.