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 (2S)-1-(4-acetyl-3,5-dimethyl-1H-pyrrol-2-yl)-2-[(4-chlorophenyl)methylsulfanyl]propan-1-one into molecular formula.
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C18H20ClNO2S
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