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 (1R,4aR,4bS,7R,9R,10aR)-1-(hydroxymethyl)-1,4a-dimethyl-7-propan-2-yl-2,3,4,4b,5,6,7,9,10,10a-decahydrophenanthren-9-ol .
user
C20H34O2
assistant