You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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1-[4-chloro-5-fluoro-2-[3-(4-methylpyrrolo[2,3-d]pyrimidin-7-yl)cyclopentyl]oxyphenyl]ethanamine is the IUPAC name of a molecule. Please give its molecular formula.
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C20H22ClFN4O
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