['CCC', 'Nc1nc(C(F)(F)F)nc(Cl)c1[N+](=O)[O-]', 'CC(C)N', 'O=[N+]([O-])c1cnc(C(F)(F)F)nc1Cl', 'FC(F)F', 'CC(C)Nc1ncnc(Cl)c1[N+](=O)[O-]']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is c1cncnc1.