You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-[1-(6-methoxyquinolin-4-yl)piperidin-4-yl]-4-(methylsulfonylmethyl)pyrrolidin-2-one The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H27N3O4S
assistant