You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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2-chloro-4-(9-fluoro-4-propan-2-yl-2,3,4,5-tetrahydro-1-benzoxepin-7-yl)-5-methylpyrimidine is the IUPAC name of a molecule. Please give its molecular formula.
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C18H20ClFN2O
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