You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
ethyl 2-[(8S,10R,13S,14S)-13-methyl-3,17-dioxo-2,6,7,8,12,14,15,16-octahydro-1H-cyclopenta[a]phenanthren-10-yl]acetate is the IUPAC name of a molecule. Please give its molecular formula.
user
C22H28O4
assistant