You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
9-hydroxy-3,5a,9-trimethyl-2-methylidene-3,3a,4,5,9a,9b-hexahydrobenzo[g][1]benzofuran-6-one The above is the IUPAC name of a molecule. Write its molecular formula.
user
C16H22O3
assistant