The entire thing.
Despite trying to ride the Justin Beiber train, he wasn't a terrible singer. Couple of pitch problems, but for the most part he was able to match pitch and hold notes.
Oh, wait. I'm supposed to be trendy, and try and fit in. So I'll say 15 seconds. That way people will think, that I think, that that music is gay and that I only listen to Wu Tang and Hathbanger.