You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(4-fluorophenyl)-[(8R)-3-imidazo[1,2-a]pyridin-2-yl-8-methyl-6,8-dihydro-5H-[1,2,4]triazolo[4,3-a]pyrazin-7-yl]methanone The above is the IUPAC name of a molecule. Write its molecular formula.
user
C20H17FN6O
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