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-[4-[5-acetyl-2-(4-fluorophenyl)-6,7-dihydro-4H-pyrazolo[1,5-a]pyrazin-3-yl]pyridin-2-yl]acetamide into its molecular formula.
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C21H20FN5O2
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