You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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3-[(4R)-3-[methyl(7H-pyrrolo[2,3-d]pyrimidin-4-yl)amino]-4-prop-2-enoylpiperidin-1-yl]-3-oxopropanenitrile is the IUPAC name of a molecule. Please give its molecular formula.
user
C18H20N6O2
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