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