f a f x a f a f a f f a a x 2.2 f a f x a f a f f a a x f a f x a f f a a x f a f x a f a f a f f a a x f a f x a f a a true f a f x a f a f a f f a a x f a f x a f a f f a a x true 2 1 a 0 1 1 f 2 0 0 1 0 1 0 0 1 0 2 1 0 f 2 1 1 1 0 2 0 0 f a f x a f a f a f f a a x f a f x a f a f a f f a a x f a f x a f a f a f f a a x true 2 1 a 0 30809 1 f 2 0 1 0 0 2 30808 1 f 2 0 0 1 0 2 0 0 f a f x a f a f a f f a a x f a f x a f f a a x false f a f x a f a a false NaTT certifiable-1.6