You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Can you give the molecular formula of the molecule (4aS,7aR)-1-cyclopentyl-4-(4-ethoxyphenyl)-6,6-dioxo-4a,5,7,7a-tetrahydro-2H-thieno[3,4-b]pyrazin-3-one ?
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C19H26N2O4S
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