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system
Provide the molecular formula for the IUPAC named substance 4-chloro-7-oxo-8H-pyrimido[5,4-b][1,4]oxazine-2-carbaldehyde;4-chloro-2-[(E)-2-phenylethenyl]-8H-pyrimido[5,4-b][1,4]oxazin-7-one;tetraoxoosmium .
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C21H14Cl2N6O9Os
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