You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 3-[1-(3-chloro-5-fluoro-2-methylphenyl)sulfonylpiperidin-4-yl]-5-methoxy-1H-indole by IUPAC nomenclature, provide its molecular formula.
user
C21H22ClFN2O3S
assistant