The melody of U Smile by Justin Bieber runs 300 notes across 50 bars, 2:44 long in Ab at 114 beats per minute. The tab sits almost entirely in the first two frets, one note at a time — no chords to barre and no strumming pattern to keep up with. A piano backing track plays the chords and bass underneath, so the line you are learning sounds like the record even at half speed.
Prefer to strum and sing it instead? U Smile chords and lyrics.