You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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3-(2-ethoxyethyl)-N-(2-methoxy-5-methylphenyl)-5-methyl-4-oxothieno[2,3-d]pyrimidine-6-carboxamide is the IUPAC name of a molecule. Please give its molecular formula.
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C20H23N3O4S
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