You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
Translate the chemical IUPAC name 2-[2-(3,4-dihydroxyphenyl)-7-hydroxychromenylium-3-yl]oxy-6-(hydroxymethyl)oxane-3,4,5-triol into its molecular formula.
user
C21H21O10+
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