(VAR N X X1 X2 XS Y YS )
(RULES 
        a__from(X) -> cons(mark(X), from(s(X)))
        a__sel(0, cons(X, XS)) -> mark(X)
        a__sel(s(N), cons(X, XS)) -> a__sel(mark(N), mark(XS))
        a__minus(X, 0) -> 0
        a__minus(s(X), s(Y)) -> a__minus(mark(X), mark(Y))
        a__quot(0, s(Y)) -> 0
        a__quot(s(X), s(Y)) -> s(a__quot(a__minus(mark(X), mark(Y)), s(mark(Y))))
        a__zWquot(XS, nil) -> nil
        a__zWquot(nil, XS) -> nil
        a__zWquot(cons(X, XS), cons(Y, YS)) -> cons(a__quot(mark(X), mark(Y)), zWquot(XS, YS))
        mark(from(X)) -> a__from(mark(X))
        mark(sel(X1, X2)) -> a__sel(mark(X1), mark(X2))
        mark(minus(X1, X2)) -> a__minus(mark(X1), mark(X2))
        mark(quot(X1, X2)) -> a__quot(mark(X1), mark(X2))
        mark(zWquot(X1, X2)) -> a__zWquot(mark(X1), mark(X2))
        mark(cons(X1, X2)) -> cons(mark(X1), X2)
        mark(s(X)) -> s(mark(X))
        mark(0) -> 0
        mark(nil) -> nil
        a__from(X) -> from(X)
        a__sel(X1, X2) -> sel(X1, X2)
        a__minus(X1, X2) -> minus(X1, X2)
        a__quot(X1, X2) -> quot(X1, X2)
        a__zWquot(X1, X2) -> zWquot(X1, X2)
        
)