(VAR X XS N Y YS X1 X2)
(RULES 
active(pairNs) -> mark(cons(0,incr(oddNs)))
active(oddNs) -> mark(incr(pairNs))
active(incr(cons(X,XS))) -> mark(cons(s(X),incr(XS)))
active(take(0,XS)) -> mark(nil)
active(take(s(N),cons(X,XS))) -> mark(cons(X,take(N,XS)))
active(zip(nil,XS)) -> mark(nil)
active(zip(X,nil)) -> mark(nil)
active(zip(cons(X,XS),cons(Y,YS))) -> mark(cons(pair(X,Y),zip(XS,YS)))
active(tail(cons(X,XS))) -> mark(XS)
active(repItems(nil)) -> mark(nil)
active(repItems(cons(X,XS))) -> mark(cons(X,cons(X,repItems(XS))))
mark(pairNs) -> active(pairNs)
mark(cons(X1,X2)) -> active(cons(mark(X1),X2))
mark(0) -> active(0)
mark(incr(X)) -> active(incr(mark(X)))
mark(oddNs) -> active(oddNs)
mark(s(X)) -> active(s(mark(X)))
mark(take(X1,X2)) -> active(take(mark(X1),mark(X2)))
mark(nil) -> active(nil)
mark(zip(X1,X2)) -> active(zip(mark(X1),mark(X2)))
mark(pair(X1,X2)) -> active(pair(mark(X1),mark(X2)))
mark(tail(X)) -> active(tail(mark(X)))
mark(repItems(X)) -> active(repItems(mark(X)))
cons(mark(X1),X2) -> cons(X1,X2)
cons(X1,mark(X2)) -> cons(X1,X2)
cons(active(X1),X2) -> cons(X1,X2)
cons(X1,active(X2)) -> cons(X1,X2)
incr(mark(X)) -> incr(X)
incr(active(X)) -> incr(X)
s(mark(X)) -> s(X)
s(active(X)) -> s(X)
take(mark(X1),X2) -> take(X1,X2)
take(X1,mark(X2)) -> take(X1,X2)
take(active(X1),X2) -> take(X1,X2)
take(X1,active(X2)) -> take(X1,X2)
zip(mark(X1),X2) -> zip(X1,X2)
zip(X1,mark(X2)) -> zip(X1,X2)
zip(active(X1),X2) -> zip(X1,X2)
zip(X1,active(X2)) -> zip(X1,X2)
pair(mark(X1),X2) -> pair(X1,X2)
pair(X1,mark(X2)) -> pair(X1,X2)
pair(active(X1),X2) -> pair(X1,X2)
pair(X1,active(X2)) -> pair(X1,X2)
tail(mark(X)) -> tail(X)
tail(active(X)) -> tail(X)
repItems(mark(X)) -> repItems(X)
repItems(active(X)) -> repItems(X)
)