So our universal set, the universe that we care about right now is integers. And let's define a subset of it. Let's call that subset, I don't know, I've been, let me put a, use a letter that I haven't been using a lot. Let's call it C. The set C, let's say it's equal to negative five, zero, and positive seven. And I'm obviously not drawing it to scale. The set of all integers is infinite, whilst the set C is a finite set. But I'll just kind of, just to draw it, that's our set C right over there.