You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule [(3aS,7aR)-3a-(hydroxymethyl)-2-methylsulfonyl-1,3,4,6,7,7a-hexahydropyrrolo[3,4-c]pyridin-5-yl]-(5-methylpyrazin-2-yl)methanone into molecular formula.
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C15H22N4O4S
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