You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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Under IUPAC nomenclature, a molecule named N-[2-(4-chlorophenoxy)ethyl]-N-methyl-4-oxopyrido[1,2-a]pyrimidine-3-carboxamide is given. What is its corresponding molecular formula?
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C18H16ClN3O3
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