You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named (4R)-1-butyl-4-[1-[(4-propan-2-ylphenyl)methyl]benzimidazol-2-yl]pyrrolidin-2-one by IUPAC nomenclature, provide its molecular formula.
user
C25H31N3O
assistant