You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named N-[(2-chlorophenyl)methyl]-N'-(2-oxo-1-azatricyclo[6.3.1.04,12]dodeca-4,6,8(12)-trien-6-yl)oxamide by IUPAC nomenclature, provide its molecular formula.
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C20H18ClN3O3
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