You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(3R,4S)-4-(3,4-dihydroxyphenyl)-3-ethoxycarbonyl-6,7-dihydroxy-3,4-dihydronaphthalene-2-carboxylic acid The above is the IUPAC name of a molecule. Write its molecular formula.
user
C20H18O8
assistant