You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named 3-[5-(4-methylphenyl)-4-oxothieno[2,3-d]pyrimidin-3-yl]-N-pyridin-4-ylpropanamide by IUPAC nomenclature, provide its molecular formula.
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C21H18N4O2S
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