b c x1 c b x1 c b x1 a a a x1 a a a a x1 b c x1 2.2 c b x1 a a x1 b c x1 c b x1 b c x1 b x1 a a a a x1 c x1 c b x1 a x1 c b x1 a a a x1 a a a a x1 b c x1 true a a a a x1 b c x1 c b x1 a a a x1 c b x1 a x1 b c x1 c b x1 a a a a x1 c x1 b c x1 b x1 c b x1 a a x1 true a 1 1 3 b 1 1 1 c 1 1 8 c 1 1 6 a 1 1 0 b 1 1 0 b c x1 c b x1 a a a a x1 b c x1 c b x1 a a a x1 NaTT certifiable-1.6