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system
Provide the molecular formula for the IUPAC named substance (6E)-2-butyl-5-imino-6-[[1-(2-methyl-5-nitrophenyl)pyrrol-2-yl]methylidene]-[1,3,4]thiadiazolo[3,2-a]pyrimidin-7-one .
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C21H20N6O3S
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