You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
3-[(E)-2-[(1S,8aS)-5,5,8a-trimethyl-2-methylidene-3,4,4a,6,7,8-hexahydro-1H-naphthalen-1-yl]ethenyl]-2-hydroxy-2H-furan-5-one The above is the IUPAC name of a molecule. Write its molecular formula.
user
C20H28O3
assistant