You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 2-(difluoromethylsulfanyl)-N-[[3-methoxy-4-(pyridin-4-ylmethoxy)phenyl]methyl]pyridine-3-carboxamide by IUPAC nomenclature, provide its molecular formula.
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C21H19F2N3O3S
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