You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
For the molecule named (2R,3S,3aR,6R,7aS)-2-(1,3-benzodioxol-5-yl)-3a,7a-dimethoxy-3-methyl-5-prop-2-enyl-2,3,6,7-tetrahydro-1-benzofuran-6-ol by IUPAC nomenclature, provide its molecular formula.
user
C21H26O6
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