The melody of I Believe by Christina Perri runs 335 notes across 60 bars, 6:42 long in A at 74 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? I Believe chords and lyrics.