You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
3-[1-[(2-fluorophenyl)methylsulfonyl]pyrrolidin-3-yl]-5-pyridin-3-yl-1,2,4-oxadiazole The above is the IUPAC name of a molecule. Write its molecular formula.
user
C18H17FN4O3S
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