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 4-chloro-5-methylpyrrolo[2,1-f][1,2,4]triazine;(4-chloropyrrolo[2,1-f][1,2,4]triazin-5-yl)methyl-triethylazanium;bromide is given. What is its corresponding molecular formula?
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C20H26BrCl2N7
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