The top of the ladder, so let's make this very clear. This distance right over here is y of t, y of t. They say at time t sub zero, y of t is 15 meters. Let me just write it here. Y of t sub zero is equal to 15 meters. Let me write this right over here. This is y of t sub zero. Let's just assume that we're drawing it at that moment, t sub zero, because I think that's going to be important.