You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
methyl (3aS)-2-oxo-6-sulfanyl-4,8b-dihydro-3H-indeno[1,2-b]furan-3a-carboxylate The above is the IUPAC name of a molecule. Write its molecular formula.
user
C13H12O4S
assistant