You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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Under IUPAC nomenclature, a molecule named (3aR,8bS)-6-bromo-3-methyl-8b-(2-methylbut-3-en-2-yl)-1,2,3a,4-tetrahydropyrrolo[2,3-b]indole is given. What is its corresponding molecular formula?
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C16H21BrN2
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