You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(3S)-3-[(2R)-3-methyl-4-oxo-2-phenylimidazolidine-1-carbonyl]-N-(2-methylpropyl)piperidine-1-carboxamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H30N4O3
assistant