You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Provide the molecular formula for the IUPAC named substance (1S,3S,8R)-N-[(2,5-difluorophenyl)methyl]-3-phenyl-2,3,5,6,7,8-hexahydro-1H-pyrrolizine-1-carboxamide .
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C21H22F2N2O
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