You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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Under IUPAC nomenclature, a molecule named 1-[(4-methylphenyl)methyl]-3-phenyl-4a,7a-dihydrothieno[3,2-d]pyrimidine-2,4-dione is given. What is its corresponding molecular formula?
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C20H18N2O2S
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