You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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Convert the IUPAC name of a molecule 6,7-dichloro-1'-methyl-N-(pyridin-4-ylmethyl)spiro[1,4-dihydroquinoxaline-3,4'-piperidine]-2-imine into molecular formula.
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C19H21Cl2N5
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