And what you might want to do after you watch it the first time-- and this isn't true just of this video, actually of all the videos-- but especially the functions, after watching it once, you might want to rewatch it and pause it right after I give you the problem and try to do it yourself, and then see-- and if you get stuck, you can play it, or if you get an answer, just you can play the video and make sure that we did the same way.