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