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 5-(2-chloro-4,5-dimethoxyphenyl)-2-(4-fluorophenyl)sulfanyl-7,8-dihydropyrimido[1,6-b]pyridazin-6-one into molecular formula.
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C21H17ClFN3O3S
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