a l x1 l a x1 r a x1 a r x1 b l x1 b a r x1 r b x1 l b x1 2.2 r a x1 r x1 a l x1 a x1 b l x1 r x1 b l x1 b a r x1 r a x1 a r x1 b l x1 a r x1 true b l x1 b a r x1 true Failed! NaTT certifiable-1.6