You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named [(3S,10R,13R,14R,17S)-14-ethyl-10,13-dimethyl-17-(6-oxopyran-3-yl)-1,2,3,6,7,8,9,11,12,15,16,17-dodecahydrocyclopenta[a]phenanthren-3-yl] N-butylcarbamate by IUPAC nomenclature, provide its molecular formula.
user
C31H45NO4
assistant