You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
2-(3-fluorophenoxy)-1-[4-(5,6,7,8-tetrahydro-[1,2,4]triazolo[4,3-a]pyrazin-3-yl)piperidin-1-yl]ethanone The above is the IUPAC name of a molecule. Write its molecular formula.
user
C18H22FN5O2
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