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 N-butan-2-yl-4-fluoro-N-[1-(4-fluorophenyl)-2,5-dioxopyrrolidin-3-yl]benzamide is given. What is its corresponding molecular formula?
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C21H20F2N2O3
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