You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-[2-[(3S,3aS,6aR)-2-methyl-3-(2-methylphenyl)-1,3,3a,4,6,6a-hexahydropyrrolo[3,4-c]pyrrol-5-yl]ethyl]pyrrolidin-2-one is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H29N3O
assistant