You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(5-chloro-2-fluorophenyl)-[4-[(3-phenyl-1,2,4-oxadiazol-5-yl)methyl]piperidin-1-yl]methanone is the IUPAC name of a molecule. Please give its molecular formula.
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C21H19ClFN3O2
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