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 2-N-(4-bromophenyl)-4-N-(4-ethylphenyl)-2-N-methyl-5-(trifluoromethyl)pyrimidine-2,4-diamine into its molecular formula.
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C20H18BrF3N4
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