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 [(3R)-3-hydroxy-3,4,4-trimethylpyrrolidin-1-yl]-[4-[(4-methylpiperazin-1-yl)methyl]phenyl]methanone .
user
C20H31N3O2
assistant