You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Please write the molecular formula of the molecule 7-ethenyl-1,1,4a,7-tetramethyl-2,3,4,5,6,9,10,10a-octahydrophenanthrene-4,4b,9,10-tetrol .
user
C20H32O4
assistant