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 methyl 1,4a-dimethyl-7-(3-oxoprop-1-enyl)-2,3,4,9,10,10a-hexahydrophenanthrene-1-carboxylate is given. What is its corresponding molecular formula?
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C21H26O3
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