Using O=c1[nH]c2cc(Br)c(Cl)c([N+](=O)[O-])c2[nH]c1=O to produce Nc1c(Cl)c(Br)cc2[nH]c(=O)c(=O)[nH]c12, please predict the agent for this reaction in SMILES notation in \boxed{$SMILES1, SMILES2, ...} format.