You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
dibismuth;1,4a-dimethyl-7-propan-2-yl-6-sulfonato-2,3,4,9,10,10a-hexahydrophenanthrene-1-carboxylate;oxygen(2-) The above is the IUPAC name of a molecule. Write its molecular formula.
user
C20H26Bi2O7S
assistant