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-(4-fluorophenyl)-3-[4-(2-methoxyphenyl)piperazin-1-ium-1-yl]pyrrolidine-2,5-dione is given. What is its corresponding molecular formula?
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C21H23FN3O3+
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