Two times three minus five, two times three minus one is five. Two times four minus one is seven. So this is two n minus one. So the area of each of these rectangles, the base is two, and the height is f of two n minus, f of two n minus one. So that's, that hopefully makes a little bit clearer, kind of mapping between the sigma notation and what we're actually trying to do. And now let's just, just for fun, let's actually try to evaluate this thing. What is this thing going to evaluate to?