You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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2-N-ethyl-4-N-methyl-4-N-[(2-methylfuran-3-yl)methyl]thieno[2,3-d]pyrimidine-2,4-diamine is the IUPAC name of a molecule. Please give its molecular formula.
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C15H18N4OS
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