(VAR N X X1 X2 XS Y YS )
(RULES 
        a__pairNs -> cons(0, incr(oddNs))
        a__oddNs -> a__incr(a__pairNs)
        a__incr(cons(X, XS)) -> cons(s(mark(X)), incr(XS))
        a__take(0, XS) -> nil
        a__take(s(N), cons(X, XS)) -> cons(mark(X), take(N, XS))
        a__zip(nil, XS) -> nil
        a__zip(X, nil) -> nil
        a__zip(cons(X, XS), cons(Y, YS)) -> cons(pair(mark(X), mark(Y)), zip(XS, YS))
        a__tail(cons(X, XS)) -> mark(XS)
        a__repItems(nil) -> nil
        a__repItems(cons(X, XS)) -> cons(mark(X), cons(X, repItems(XS)))
        mark(pairNs) -> a__pairNs
        mark(incr(X)) -> a__incr(mark(X))
        mark(oddNs) -> a__oddNs
        mark(take(X1, X2)) -> a__take(mark(X1), mark(X2))
        mark(zip(X1, X2)) -> a__zip(mark(X1), mark(X2))
        mark(tail(X)) -> a__tail(mark(X))
        mark(repItems(X)) -> a__repItems(mark(X))
        mark(cons(X1, X2)) -> cons(mark(X1), X2)
        mark(0) -> 0
        mark(s(X)) -> s(mark(X))
        mark(nil) -> nil
        mark(pair(X1, X2)) -> pair(mark(X1), mark(X2))
        a__pairNs -> pairNs
        a__incr(X) -> incr(X)
        a__oddNs -> oddNs
        a__take(X1, X2) -> take(X1, X2)
        a__zip(X1, X2) -> zip(X1, X2)
        a__tail(X) -> tail(X)
        a__repItems(X) -> repItems(X)
        
)