You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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Under IUPAC nomenclature, a molecule named 2-[4-[2-(5-chloro-2,4-dimethoxyphenyl)imidazo[1,2-a]pyridin-7-yl]piperazin-1-yl]acetonitrile is given. What is its corresponding molecular formula?
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C21H22ClN5O2
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