(VAR x y) (RULES app(pred, app(s, x)) -> x app(app(minus, x), 0) -> x app(app(minus, x), app(s, y)) -> app(pred, app(app(minus, x), y)) app(app(quot, 0), app(s, y)) -> 0 app(app(quot, app(s, x)), app(s, y)) -> app(s, app(app(quot, app(app(minus, x), y)), app(s, y))) )