You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 3-N-[4-(diethylamino)phenyl]-5-N-[(4-methylphenyl)methyl]-1,2,4-triazine-3,5-diamine by IUPAC nomenclature, provide its molecular formula.
user
C21H26N6
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