You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Translate the chemical IUPAC name (2R)-2-[4-[methyl(methylsulfonyl)amino]phenoxy]-N-[4-(2-oxopyrrolidin-1-yl)phenyl]propanamide into its molecular formula.
user
C21H25N3O5S
assistant