You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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Translate the chemical IUPAC name 2-[(2,4-dichlorophenyl)methyl]-6-methyl-5-(4-methylphenyl)-3H-thieno[2,3-d]pyrimidin-4-one into its molecular formula.
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C21H16Cl2N2OS
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