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 9-(1-fluorocyclobutanecarbonyl)-1-methyl-4-(pyridin-3-ylmethyl)-1,4,9-triazaspiro[5.5]undecan-5-one .
user
C20H27FN4O2
assistant