You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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2-[5-(3-cyclopropyl-1-methyl-6-oxo-5,7-dihydro-4H-pyrazolo[3,4-b]pyridin-4-yl)furan-2-yl]benzonitrile is the IUPAC name of a molecule. Please give its molecular formula.
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C21H18N4O2
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