def ArestasExtremas(self, S):
        extremos = []
        for i in S:
            for j in S:
                if i == j:
                    continue
                for k in S:
                    if k == i and k == j:
                        continue
                if not(LeftOn(i, j, k)):
                    pass
                extremos.append([i,j])
        return extremos