You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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Translate the chemical IUPAC name methyl (4aS,8aR)-3-cyano-1,1,4a-trimethyl-2,6-dioxo-4,7,8,9,10,10a-hexahydro-3H-phenanthrene-8a-carboxylate into its molecular formula.
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C20H25NO4
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