You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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Convert the IUPAC name of a molecule 3-[1-(2-ethylbutanoyl)piperidin-4-yl]-8-propyl-1,3,8-triazaspiro[4.5]decane-2,4-dione into molecular formula.
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C21H36N4O3
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