You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-(2,6-dimethylphenyl)-2-[5-(5-methylthiophen-2-yl)-4-oxothieno[2,3-d]pyrimidin-3-yl]acetamide is the IUPAC name of a molecule. Please give its molecular formula.
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C21H19N3O2S2
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