You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(9R,10R,13S)-10,13-dimethyl-2,3,6,7,9,11,12,15,16,17-decahydro-1H-cyclopenta[a]phenanthrene-3,17-diol is the IUPAC name of a molecule. Please give its molecular formula.
user
C19H28O2
assistant