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