You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named 3-amino-6-[[3-[[[2-(4-aminophenyl)sulfanylacetyl]amino]methyl]phenyl]methyl]pyrazine-2-carboxamide by IUPAC nomenclature, provide its molecular formula.
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C21H22N6O2S
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