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