Using O=C(Cl)c1cc(Cl)cc(Cl)c1Cl, O=C1NC(=O)c2c(Br)c(Br)c(Br)c(Br)c21 to produce O=C(c1cc(Cl)cc(Cl)c1Cl)N1C(=O)c2c(Br)c(Br)c(Br)c(Br)c2C1=O, please predict the agent for this reaction in SMILES notation in \boxed{$SMILES1, SMILES2, ...} format.