You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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Translate the chemical IUPAC name 1-O-tert-butyl 1-O'-methyl 5-bromo-4-chloro-1'-methylspiro[2H-pyrrolo[2,3-b]pyridine-3,4'-cyclohexane]-1,1'-dicarboxylate into its molecular formula.
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C20H26BrClN2O4
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