You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(8R,9R,10S,13R,14R,17R)-10-(hydroxymethyl)-13-methyl-3-oxo-1,2,6,7,8,9,11,12,14,15,16,17-dodecahydrocyclopenta[a]phenanthrene-17-carboxylic acid is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H28O4
assistant