You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(3S)-1-ethyl-3-methyl-4-[3-([1,2,4]triazolo[4,3-a]pyrimidin-6-yl)benzoyl]piperazin-2-one is the IUPAC name of a molecule. Please give its molecular formula.
user
C19H20N6O2
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