You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(2-chloro-3-methylphenyl)-(6-methyl-1-pyrazin-2-yl-6,7-dihydro-4H-triazolo[4,5-c]pyridin-5-yl)methanone is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H17ClN6O
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