You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(2R)-2-[(1R,2R,6R,7R)-3,5-dioxo-4-azatricyclo[5.2.2.02,6]undec-8-en-4-yl]-N-(3-methylphenyl)butanamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H24N2O3
assistant