You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named (3R)-1-[(4-chlorophenyl)methyl]-6-oxo-N-[[4-(trifluoromethyl)phenyl]methyl]piperidine-3-carboxamide by IUPAC nomenclature, provide its molecular formula.
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C21H20ClF3N2O2
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