You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 1-[1-(3-chloro-4-fluoroanilino)-1-oxopropan-2-yl]-N-phenylpiperidine-3-carboxamide by IUPAC nomenclature, provide its molecular formula.
user
C21H23ClFN3O2
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