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