You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 4-(5-chloro-N-methylsulfonyl-2-phenoxyanilino)-N-[2-(4-chlorophenyl)ethyl]butanamide by IUPAC nomenclature, provide its molecular formula.
user
C25H26Cl2N2O4S
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