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Under IUPAC nomenclature, a molecule named 1-[(9R,9aS)-9-pyrrolidin-1-yl-3,4,6,8,9,9a-hexahydro-2H-[1,3]oxazino[3,4-b][1,2,4]triazin-1-yl]-2-(3,4-dichlorophenyl)ethanone is given. What is its corresponding molecular formula?
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C18H24Cl2N4O2
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