You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Convert the IUPAC name of a molecule (1S,2R,4aS,4bS,5R,8aS)-2-ethenyl-2,4b,8,8-tetramethyl-3,4,4a,5,6,7,8a,9-octahydro-1H-phenanthrene-1,5-diol into molecular formula.
user
C20H32O2
assistant