You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named (4S)-3-[(2R,3S)-2,3-dimethyl-2-phenylcyclopropanecarbonyl]-4-phenyl-1,3-oxazolidin-2-one by IUPAC nomenclature, provide its molecular formula.
user
C21H21NO3
assistant