f x f a a f f x a x 2.2 f x f a a f x a f x f a a f f x a x true f x f a a f f x a x true 2 1 a 0 2 1 f 2 0 1 0 0 1 0 1 0 0 2 1 32278 f 2 1 1 1 1 1 0 0 1 1 2 0 0 f x f a a f f x a x f x f a a f x a false NaTT certifiable-1.6