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 (1S)-1-[(1S,4E,7aS)-4-(bromomethylidene)-7a-methyl-2,3,3a,5,6,7-hexahydro-1H-inden-1-yl]ethanol into its molecular formula.
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C13H21BrO
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