You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule 2-[8-chloro-1,4-dimethyl-3-[(4-methylsulfonylphenyl)methyl]-2-oxoquinolin-5-yl]oxyacetic acid into molecular formula.
user
C21H20ClNO6S
assistant