Just to give credit where credit is due, the song was written by the late Fred Neil, though it was done in the movie by Harry Nilsson, apparently because of some contract problems. Lyrics here (can't vouch for those chords), and a fascinating short biography of Fred Neil here, from Rolling Stone. I never knew that the "Pooneil" of "Ballad of You and Me and Pooneil" and "The House at Pooneil Corner" was Fred Neil. I loved his stuff back in the late 60's, especially The Dolphins. An underappreciated talent, in my opinion.

Aloha,
Mark