You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Name the molecular formula for the molecule established as 4-(3,4-difluoro-N-methylsulfonylanilino)-N-[2-[(2-methylphenyl)methylsulfanyl]ethyl]butanamide using the IUPAC nomenclature.
user
C21H26F2N2O3S2
assistant