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What is the molecular formula of the molecule (4aS,7aR)-1-[2-(4-fluorophenyl)ethyl]-4-(4-methoxyphenyl)-6,6-dioxo-4a,5,7,7a-tetrahydro-2H-thieno[3,4-b]pyrazin-3-one ?
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C21H23FN2O4S
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