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 5-bromo-2-[3-oxo-3-[4-(2-oxo-2-pyrrolidin-1-ylethyl)piperazin-1-yl]propyl]isoindole-1,3-dione is given. What is its corresponding molecular formula?
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C21H25BrN4O4
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