You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named (3R)-3-[2-oxo-2-(3-propan-2-yl-6,8-dihydro-5H-[1,2,4]triazolo[4,3-a]pyrazin-7-yl)ethyl]-3H-2-benzofuran-1-one by IUPAC nomenclature, provide its molecular formula.
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C18H20N4O3
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