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