You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
(3S,6R)-2-(hydroxymethyl)-6-[3-(5-nitro-2,3-dihydroindol-1-yl)phenoxy]oxane-3,4,5-triol is the IUPAC name of a molecule. Please give its molecular formula.
user
C20H22N2O8
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