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