You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
[(2R,3R,4R,5S)-3,4-diacetyloxy-6-bromo-5-(1,3-dioxoisoindol-2-yl)oxan-2-yl]methyl acetate is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H20BrNO9
assistant