You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named (3-bromo-1-methylindol-2-yl)-(4-pyrrolidin-1-ylsulfonylpiperazin-1-yl)methanone by IUPAC nomenclature, provide its molecular formula.
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C18H23BrN4O3S
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