You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Please write the molecular formula of the molecule (5S,9S)-2-[2-(dimethylamino)ethyl]-7-(oxolan-3-yl)-9-phenyl-2,7-diazaspiro[4.4]nonan-1-one .
user
C21H31N3O2
assistant