You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named methyl (1S,3S,7S,12R,15R,16S,17S,18R,20E)-12-(3,4-dihydroxyphenyl)-20-ethylidene-16,17,18-trihydroxy-9-oxo-2,4,10,13,19-pentaoxatricyclo[13.3.1.13,7]icos-5-ene-6-carboxylate by IUPAC nomenclature, provide its molecular formula.
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C25H30O13
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