You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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Translate the chemical IUPAC name N-benzyl-2-[7-(4-chlorophenyl)-2-methyl-4-oxo-[1,3]thiazolo[4,5-d]pyridazin-5-yl]acetamide into its molecular formula.
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C21H17ClN4O2S
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