You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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(5R)-6,6-difluoro-5-(2-fluoro-5-pyrimidin-5-ylphenyl)-5,7,7-trimethyl-1,4-oxazepan-3-one is the IUPAC name of a molecule. Please give its molecular formula.
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C18H18F3N3O2
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