(VAR X XS N Y)
(RULES 
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))
tail(cons(X)) -> XS
repItems(nil) -> nil
repItems(cons(X)) -> cons(X)
)