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