['Fc1ccccc1', 'O=CNNS(=O)(=O)c1ccc(F)c(C(F)(F)F)c1', 'FC(F)F', 'O=C(NNS(=O)(=O)c1ccc(F)cc1)c1ccc(F)cc1']
The Murcko scaffold (minmal number of connected rings) of <smiles></smiles> is O=C(NNS(=O)(=O)c1ccccc1)c1ccccc1.