You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-O-methyl 2-O-[2-(1-methylsulfonyl-3,4-dihydro-2H-quinolin-6-yl)-2-oxoethyl] benzene-1,2-dicarboxylate is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H21NO7S
assistant