a x1 b b x1 a b b x1 b b c c c a x1 b b x1 c c c x1 c c c b b x1 a x1 2.2 a b b x1 b c c c a x1 a b b x1 a x1 b b x1 c x1 a x1 b x1 c c c b b x1 a x1 b b x1 c c c x1 a x1 b b x1 a b b x1 c a x1 a b b x1 c c c a x1 a b b x1 b b c c c a x1 b b x1 c c x1 a b b x1 c c a x1 true a b b x1 c c a x1 c c c b b x1 a x1 b b x1 c c x1 a b b x1 b b c c c a x1 a b b x1 c c c a x1 a x1 b x1 b b x1 c x1 a b b x1 a x1 a b b x1 c a x1 a x1 b b x1 b b x1 c c c x1 a b b x1 b c c c a x1 true a 1 1 8 b 1 1 4 c 1 1 0 c 1 1 0 a 1 1 6 b 1 1 0 c c c b b x1 a x1 a x1 b b x1 b b x1 c c c x1 a b b x1 b b c c c a x1 NaTT certifiable-1.6