(VAR X X1 X2 Y )
(RULES 
        a__nats -> a__adx(a__zeros)
        a__zeros -> cons(0, zeros)
        a__incr(cons(X, Y)) -> cons(s(X), incr(Y))
        a__adx(cons(X, Y)) -> a__incr(cons(X, adx(Y)))
        a__hd(cons(X, Y)) -> mark(X)
        a__tl(cons(X, Y)) -> mark(Y)
        mark(nats) -> a__nats
        mark(adx(X)) -> a__adx(mark(X))
        mark(zeros) -> a__zeros
        mark(incr(X)) -> a__incr(mark(X))
        mark(hd(X)) -> a__hd(mark(X))
        mark(tl(X)) -> a__tl(mark(X))
        mark(cons(X1, X2)) -> cons(X1, X2)
        mark(0) -> 0
        mark(s(X)) -> s(X)
        a__nats -> nats
        a__adx(X) -> adx(X)
        a__zeros -> zeros
        a__incr(X) -> incr(X)
        a__hd(X) -> hd(X)
        a__tl(X) -> tl(X)
        
)