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