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 (2R,5R)-2-[2-fluoro-3-(2-fluorophenyl)phenyl]-7-methyl-1,7-diazaspiro[4.4]nonan-6-one .
user
C20H20F2N2O
assistant