sub 0 0 0 sub s x 0 s x sub 0 s x 0 sub s x s y sub x y zero nil zero2 0 nil zero cons x xs zero2 sub x x cons x xs zero2 0 nil nil zero2 0 cons x xs cons sub x x zero xs zero2 s y nil zero nil zero2 s y cons x xs zero cons x xs sub 2 0 0 s 1 zero 1 nil 0 zero2 2 cons 2 FULL ./AProVE_09_Inductive/zerolist.trs