You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named (3R)-1-butyl-N-[4-[ethyl-(3-methylphenyl)carbamoyl]phenyl]-5-oxopyrrolidine-3-carboxamide by IUPAC nomenclature, provide its molecular formula.
user
C25H31N3O3
assistant