You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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Translate the chemical IUPAC name 7-[(4aS,7aS)-2,3,4,4a,5,7a-hexahydro-1H-pyrrolo[3,4-b]pyridin-6-ium-6-yl]-1-cyclopropyl-6-fluoro-8-methoxy-4-oxo-2,3,7,8-tetrahydroquinoline-3-carboxylic acid;hydrochloride into its molecular formula.
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C21H28ClFN3O4+
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