You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
ethane;3,5,13-trimethyl-1,2,3,4,6,7,8,9,10,11,12,14,15,16-tetradecahydrocyclopenta[a]phenanthren-17-one The above is the IUPAC name of a molecule. Write its molecular formula.
user
C22H38O
assistant