You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule N-(4-cyanophenyl)-2-[[(7S)-7-methyl-5,6,7,8-tetrahydro-[1]benzothiolo[2,3-d]pyrimidin-4-yl]sulfanyl]acetamide into molecular formula.
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C20H18N4OS2
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