You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Translate the chemical IUPAC name 3-(3-methylbutyl)-8-[4-(2-oxopyrrolidin-1-yl)butanoyl]-1-oxa-3,8-diazaspiro[4.5]decan-2-one into its molecular formula.
user
C20H33N3O4
assistant