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