a x1 b x1 a b x1 x1 c c b x1 b c a c c x1 2.2 c c b x1 a c c x1 c c b x1 c c x1 c c b x1 c a c c x1 c c b x1 c x1 true c c b x1 c x1 c c b x1 c a c c x1 c c b x1 c c x1 true Failed! NaTT certifiable-1.6