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