You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 1-[(2,4-dichlorophenyl)methylsulfonyl]-N-[(4-methoxyphenyl)methyl]piperidine-4-carboxamide by IUPAC nomenclature, provide its molecular formula.
user
C21H24Cl2N2O4S
assistant