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 (6-bromo-1,3,4,5-tetrahydropyrido[4,3-b]indol-2-yl)-(1-butylsulfonylpiperidin-4-yl)methanone into molecular formula.
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C21H28BrN3O3S
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