There are two ways to play this song

Version with CAPO on 2nd

whole song is just 

Am, C, F

apart from the bridge before the chorus where he sings "and then you came and you.....", which is

Em, F


Version with no CAPO

whole song is just 

Bm, D, G

apart from the bridge before the chorus where he sings "and then you came and you.....", which is

F#m, G


Hope this helps, please rate!!