You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
What is the molecular formula of the molecule identified by methyl (3S)-2-[2-(2,4-dioxo-1,3-diazaspiro[4.4]nonan-3-yl)acetyl]-3,4-dihydro-1H-isoquinoline-3-carboxylate ?
user
C20H23N3O5
assistant