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 (3R,3aS,5aR,9aS,9bS)-5a-methyl-9-methylidene-1'-(4-methylpent-3-enyl)spiro[3a,4,5,6,7,8,9a,9b-octahydrobenzo[g][1]benzofuran-3,4'-cyclohexene]-2-one ?
user
C25H36O2
assistant