You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named (8aR)-2-(2,5-dimethoxyphenyl)sulfonyl-3,4,6,7,8,8a-hexahydro-1H-pyrrolo[1,2-a]pyrazine by IUPAC nomenclature, provide its molecular formula.
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C15H22N2O4S
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