You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(4R,5R)-9-[(4-methoxyphenyl)methyl]-4-pyridin-3-yl-6-oxa-2,9-diazaspiro[4.5]decan-10-one The above is the IUPAC name of a molecule. Write its molecular formula.
user
C20H23N3O3
assistant