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