f x f a f f a a a f f a x x 2.2 f x f a f f a a a f a x f x f a f f a a a f f a x x true f x f a f f a a a f f a x x f x f a f f a a a f a x true a 0 2438 f 2 2439 f 2 1 2 0 f x f a f f a a a f f a x x f x f a f f a a a f f a x x f x f a f f a a a f f a x x true Failed! NaTT certifiable-1.6