You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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N-ethyl-N-(2-methylprop-2-enyl)-3-(3-pyridin-4-yl-1,2,4-oxadiazol-5-yl)propanamide is the IUPAC name of a molecule. Please give its molecular formula.
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C16H20N4O2
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