You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named ethyl 6,7-dichloro-3-[4-(2-methoxy-2-oxoacetyl)piperazin-1-yl]quinoxaline-2-carboxylate by IUPAC nomenclature, provide its molecular formula.
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C18H18Cl2N4O5
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