You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named 5-[5-[(2,6-dichloro-3-fluorophenyl)methyl]-2-methyl-1,6,7,8-tetrahydropyrazino[2,3-c]pyridazin-3-yl]-3-piperidin-4-yl-1,2,4-oxadiazole by IUPAC nomenclature, provide its molecular formula.
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C21H24Cl2FN7O
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