You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named 1-[(4R,5S)-4-methoxy-7-azaspiro[4.5]decan-7-yl]-3-pyridin-3-ylpropan-1-one by IUPAC nomenclature, provide its molecular formula.
user
C18H26N2O2
assistant