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