You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Can you give the molecular formula of the molecule (1R,4aS,7S,8aS,10aR)-7-ethenyl-10a-hydroxy-1,4a,7-trimethyl-2,3,4,6,8,8a,9,10-octahydrophenanthrene-1-carboxylic acid ?
user
C20H30O3
assistant