You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Translate the chemical IUPAC name (8R,9R,10R,11S,13S,14R,17S)-11,17-dihydroxy-10,13,17-trimethyl-3-oxo-7,8,9,11,12,14,15,16-octahydro-6H-cyclopenta[a]phenanthrene-2-carbaldehyde into its molecular formula.
user
C21H28O4
assistant