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