Assume that on an island, people can be divided only into 2 groups : good guys and bad guys. People who are good guys always tell the truth. On the other hand, people who are bad guys always lie. Nobita visits the island and is approached by 2 natives (A and B) who speak as follows: A says : B is a good guy. B says : A and I are of opposite type. Use your knowledge about Logic and proof techniques to help Nobita derive what A and B are.