You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(5S,8S,9S,10S,13R,14S,17S)-17-ethyl-10,13-dimethyl-1,2,4,5,6,7,8,9,11,12,14,15,16,17-tetradecahydrocyclopenta[a]phenanthren-3-one The above is the IUPAC name of a molecule. Write its molecular formula.
user
C21H34O
assistant