You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule 2-(4-amino-5,6-dimethylthieno[2,3-d]pyrimidin-2-yl)sulfanyl-N-methyl-N-phenylpropanamide into molecular formula.
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C18H20N4OS2
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