You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
cyclopentane;10,13-dimethyl-17-propanoyl-6,7,8,9,11,12,14,15,16,17-decahydrocyclopenta[a]phenanthren-3-one;ethane;ethene is the IUPAC name of a molecule. Please give its molecular formula.
user
C31H50O2
assistant