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