You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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Under IUPAC nomenclature, a molecule named (3S)-1-(3-chlorophenyl)-3-(4-fluorophenyl)-2,5,6,7,8,9-hexahydroimidazo[1,2-a]azepin-4-ium-3-ol is given. What is its corresponding molecular formula?
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C20H21ClFN2O+
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