You are a chemist. Please follow the instructions to convert the structure to the corresponding name.
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For the molecule named 3a-methyl-4-[4-[4-[(2-methylphenyl)methyl]piperazin-1-yl]-4-oxobutyl]-2,3-dihydropyrrolo[1,2-a]quinazoline-1,5-dione by IUPAC nomenclature, provide its molecular formula.
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C28H34N4O3
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