You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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Under IUPAC nomenclature, a molecule named 15-chloro-16,18-dihydroxy-4-methyl-3-oxabicyclo[12.4.0]octadeca-1(14),6,15,17-tetraene-2,12-dione is given. What is its corresponding molecular formula?
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C18H21ClO5
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