You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(7S)-1-benzyl-7-propan-2-yl-2,3,4,4a,5,6,7,7a-octahydropyrrolo[3,4-b]pyridine is the IUPAC name of a molecule. Please give its molecular formula.
user
C17H26N2
assistant