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Name the molecular formula for the molecule established as 4-ethyl-5-fluoro-2-[5-(pyridine-3-carbonyl)-1,3,3a,4,6,6a-hexahydropyrrolo[3,4-c]pyrrol-2-yl]-1H-pyrimidin-6-one using the IUPAC nomenclature.
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C18H20FN5O2
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