You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(E)-3-[5-chloro-1-(3-chlorophenyl)-3-methylpyrazol-4-yl]-2-(6,7,8,9-tetrahydro-5H-[1,2,4]triazolo[4,3-a]azepin-3-yl)prop-2-enenitrile is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H18Cl2N6
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