You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
1-[4-chloro-3-(trifluoromethyl)phenyl]sulfonyl-N-[2-(3-fluorophenyl)ethyl]piperidine-4-carboxamide The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H21ClF4N2O3S
assistant