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