You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-[(2S)-2-(1,3-benzothiazol-2-yl)pyrrolidin-1-yl]-1-(6,7-dihydro-4H-thieno[3,2-c]pyridin-5-yl)ethanone is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H21N3OS2
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