You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named N-cyclohexyl-5-fluoro-2-(5-fluoro-1-methyl-7,7a-dihydropyrrolo[2,3-b]pyridin-3-yl)pyrimidin-4-amine by IUPAC nomenclature, provide its molecular formula.
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C18H21F2N5
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