You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-[2-[(3R)-3-methylpiperidin-1-yl]-2-oxoethyl]sulfanyl-N-(6-methyl-3-prop-2-enyl-1,3-benzothiazol-2-ylidene)acetamide is the IUPAC name of a molecule. Please give its molecular formula.
user
C21H27N3O2S2
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