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