You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Under IUPAC nomenclature, a molecule named [9-(oxan-4-ylmethyl)-3,9-diazaspiro[5.5]undecan-3-yl]-pyridin-3-ylmethanone is given. What is its corresponding molecular formula?
user
C21H31N3O2
assistant