You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
system
N-(3-chloro-4-fluorophenyl)-8-methoxy-5,6-dihydropyrimido[4,5-b][1,4]benzoxazepin-4-amine is the IUPAC name of a molecule. Please give its molecular formula.
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C18H14ClFN4O2
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