The melody of Till The World Ends by Britney Spears runs 421 notes across 55 bars, 3:11 long in Ab at 132 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? Till The World Ends chords and lyrics.