You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named propan-2-yl (7R)-7-(5-bromo-2-ethoxyphenyl)-5-methyl-4,7-dihydro-[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxylate by IUPAC nomenclature, provide its molecular formula.
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C18H21BrN4O3
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