You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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Convert the IUPAC name of a molecule 1-[4-[1-(1,3-benzothiazol-2-yl)ethyl]piperazin-1-yl]-2-(2,4-difluorophenoxy)ethanone into molecular formula.
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C21H21F2N3O2S
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