You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-[(2-chlorophenyl)methyl]-3-[[(1,1-dioxothiolan-3-yl)amino]methyl]-7-fluoroquinolin-2-one is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H20ClFN2O3S
assistant