You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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Convert the IUPAC name of a molecule 7-(4-bromo-2-fluoroanilino)-N-(2-methoxyethyl)-5-oxo-2,3-dihydro-1H-indolizine-8-carboxamide into molecular formula.
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C18H19BrFN3O3
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