g h g x g x g g x g h g x h h x h f h x x 2.2 g g x h g x h h x h f h x x g g x g h g x true g g x g h g x true h 1 1 f 2 2 1 h 1 0 g 1 1 0 g 1 1 2 h h x h f h x x g g x h g x false h h x h f h x x false NaTT certifiable-1.6