You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named N-[(3S,7S,8aS)-3-[(1R)-1-hydroxyethyl]-1,4-dioxo-2,3,6,7,8,8a-hexahydropyrrolo[1,2-a]pyrazin-7-yl]pyridine-3-carboxamide by IUPAC nomenclature, provide its molecular formula.
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C15H18N4O4
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