(VAR N X XS Y )
(RULES 
        tail(cons(X)) -> XS
        pairNs -> cons(0)
        oddNs -> incr(pairNs)
        incr(cons(X)) -> cons(s(X))
        take(0, XS) -> nil
        take(s(N), cons(X)) -> cons(X)
        zip(nil, XS) -> nil
        zip(X, nil) -> nil
        zip(cons(X), cons(Y)) -> cons(pair(X, Y))
        repItems(nil) -> nil
        repItems(cons(X)) -> cons(X)
        
)