(VAR L X X1 X2 XS Y YS )
(RULES 
        a__app(nil, YS) -> mark(YS)
        a__app(cons(X, XS), YS) -> cons(mark(X), app(XS, YS))
        a__from(X) -> cons(mark(X), from(s(X)))
        a__zWadr(nil, YS) -> nil
        a__zWadr(XS, nil) -> nil
        a__zWadr(cons(X, XS), cons(Y, YS)) -> cons(a__app(mark(Y), cons(mark(X), nil)), zWadr(XS, YS))
        a__prefix(L) -> cons(nil, zWadr(L, prefix(L)))
        mark(app(X1, X2)) -> a__app(mark(X1), mark(X2))
        mark(from(X)) -> a__from(mark(X))
        mark(zWadr(X1, X2)) -> a__zWadr(mark(X1), mark(X2))
        mark(prefix(X)) -> a__prefix(mark(X))
        mark(nil) -> nil
        mark(cons(X1, X2)) -> cons(mark(X1), X2)
        mark(s(X)) -> s(mark(X))
        a__app(X1, X2) -> app(X1, X2)
        a__from(X) -> from(X)
        a__zWadr(X1, X2) -> zWadr(X1, X2)
        a__prefix(X) -> prefix(X)
        
)