You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(2R)-N-[2-[(2-chloro-6-fluorophenyl)methylsulfanyl]ethyl]-2-(4-ethoxy-N-methylsulfonylanilino)propanamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H26ClFN2O4S2
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