It's not 100% correct because it later adds a second guitar that does another riff but 
to me this would be the main riff of the song and it's repeated during the whole song 
including the intro:


                |decrescendo->
e|---3----3--2---0-3----------|
B|---3----3--2-------0-2------|
G|---0----0--0-----------0----|  BIS
D|-------------------------0--|
A|-----------0----------------|
E|-0----0---------------------|