lt0 Nil Cons x' xs True lt0 Cons x' xs' Cons x xs lt0 xs' xs g x Nil Cons Nil Cons Nil Cons Nil Cons Nil Nil f x Nil Cons Nil Cons Nil Cons Nil Cons Nil Nil notEmpty Cons x xs True notEmpty Nil False lt0 x Nil False g x Cons x' xs g[Ite][False][Ite] lt0 x Cons Nil Nil x Cons x' xs f x Cons x' xs f[Ite][False][Ite] lt0 x Cons Nil Nil x Cons x' xs number4 n Cons Nil Cons Nil Cons Nil Cons Nil Nil goal x y Cons f x y Cons g x y Nil g[Ite][False][Ite] False Cons x xs y g xs Cons Cons Nil Nil y g[Ite][False][Ite] True x' Cons x xs g x' xs f[Ite][False][Ite] False Cons x xs y f xs Cons Cons Nil Nil y f[Ite][False][Ite] True x' Cons x xs f x' xs f[Ite][False][Ite] 3 True 0 Nil 0 lt0 2 g 2 f 2 g[Ite][False][Ite] 3 Cons 2 number4 1 notEmpty 1 goal 2 False 0 INNERMOST