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What is the molecular formula of the molecule 20-bromo-7,9-dimethyl-3,7,9,13-tetrazahexacyclo[13.7.1.02,13.04,12.06,10.019,23]tricosa-1(23),2,4,6(10),11,15,17,19,21-nonaene-8,14-dione ?
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C21H13BrN4O2
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