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 (1R,3R,4aR,4bS,7R,10aR)-7-ethenyl-1-(hydroxymethyl)-1,4a,7-trimethyl-3,4,4b,5,6,9,10,10a-octahydro-2H-phenanthren-3-ol ?
user
C20H32O2
assistant