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 6-[2-(4-butylphenyl)-2-oxoethyl]-5,6,7,8-tetrahydro-2H-cinnolin-3-one is given. What is its corresponding molecular formula?
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C20H24N2O2
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