f a f a x f a f x f f a a a 2.2 f a f a x f x f f a a a f a f a x f f a a a f a f a x f a f x f f a a a f a f a x f a a true f a f a x f a f x f f a a a true 2 1 a 0 1 2 f 2 0 0 1 0 1 0 0 1 0 2 7629 1 f 2 2 0 0 f a f a x f a f x f f a a a f a f a x f a a false f a f a x f f a a a false f a f a x f x f f a a a false NaTT certifiable-1.6