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