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