You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
5-[(2,5-difluorophenyl)-(4-fluorophenyl)sulfonylmethyl]-N-methoxy-4-methylpyridine-2-carboxamide The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H17F3N2O4S
assistant