You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(2R,3R,4R,5S,6R)-6-[2-[(1S,3S,4aR,10aR)-4a-[[(1R,3R,4aS,10aS)-9,10a-dihydroxy-3-(2-methoxy-2-oxoethyl)-1-methyl-5,10-dioxo-3,4-dihydro-1H-benzo[g]isochromen-4a-yl]sulfanyl]-9,10a-dihydroxy-1-methyl-5,10-dioxo-3,4-dihydro-1H-benzo[g]isochromen-3-yl]acetyl]oxy-3,4,5-trihydroxyoxane-2-carboxylic acid is the IUPAC name of a molecule. Please give its molecular formula.
user
C39H40O20S
assistant