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 6-bromo-5-methyl-3-(2-methyl-3-oxobutan-2-yl)-1H-thieno[2,3-d]pyrimidine-2,4-dione into its molecular formula.
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C12H13BrN2O3S
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