(VAR N X X1 X2 X3 X4 XS YS ZS )
(RULES 
        active(natsFrom(N)) -> mark(cons(N, natsFrom(s(N))))
        active(fst(pair(XS, YS))) -> mark(XS)
        active(snd(pair(XS, YS))) -> mark(YS)
        active(splitAt(0, XS)) -> mark(pair(nil, XS))
        active(splitAt(s(N), cons(X, XS))) -> mark(u(splitAt(N, XS), N, X, XS))
        active(u(pair(YS, ZS), N, X, XS)) -> mark(pair(cons(X, YS), ZS))
        active(head(cons(N, XS))) -> mark(N)
        active(tail(cons(N, XS))) -> mark(XS)
        active(sel(N, XS)) -> mark(head(afterNth(N, XS)))
        active(take(N, XS)) -> mark(fst(splitAt(N, XS)))
        active(afterNth(N, XS)) -> mark(snd(splitAt(N, XS)))
        mark(natsFrom(X)) -> active(natsFrom(mark(X)))
        mark(cons(X1, X2)) -> active(cons(mark(X1), X2))
        mark(s(X)) -> active(s(mark(X)))
        mark(fst(X)) -> active(fst(mark(X)))
        mark(pair(X1, X2)) -> active(pair(mark(X1), mark(X2)))
        mark(snd(X)) -> active(snd(mark(X)))
        mark(splitAt(X1, X2)) -> active(splitAt(mark(X1), mark(X2)))
        mark(0) -> active(0)
        mark(nil) -> active(nil)
        mark(u(X1, X2, X3, X4)) -> active(u(mark(X1), X2, X3, X4))
        mark(head(X)) -> active(head(mark(X)))
        mark(tail(X)) -> active(tail(mark(X)))
        mark(sel(X1, X2)) -> active(sel(mark(X1), mark(X2)))
        mark(afterNth(X1, X2)) -> active(afterNth(mark(X1), mark(X2)))
        mark(take(X1, X2)) -> active(take(mark(X1), mark(X2)))
        natsFrom(mark(X)) -> natsFrom(X)
        natsFrom(active(X)) -> natsFrom(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)
        s(mark(X)) -> s(X)
        s(active(X)) -> s(X)
        fst(mark(X)) -> fst(X)
        fst(active(X)) -> fst(X)
        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)
        snd(mark(X)) -> snd(X)
        snd(active(X)) -> snd(X)
        splitAt(mark(X1), X2) -> splitAt(X1, X2)
        splitAt(X1, mark(X2)) -> splitAt(X1, X2)
        splitAt(active(X1), X2) -> splitAt(X1, X2)
        splitAt(X1, active(X2)) -> splitAt(X1, X2)
        u(mark(X1), X2, X3, X4) -> u(X1, X2, X3, X4)
        u(X1, mark(X2), X3, X4) -> u(X1, X2, X3, X4)
        u(X1, X2, mark(X3), X4) -> u(X1, X2, X3, X4)
        u(X1, X2, X3, mark(X4)) -> u(X1, X2, X3, X4)
        u(active(X1), X2, X3, X4) -> u(X1, X2, X3, X4)
        u(X1, active(X2), X3, X4) -> u(X1, X2, X3, X4)
        u(X1, X2, active(X3), X4) -> u(X1, X2, X3, X4)
        u(X1, X2, X3, active(X4)) -> u(X1, X2, X3, X4)
        head(mark(X)) -> head(X)
        head(active(X)) -> head(X)
        tail(mark(X)) -> tail(X)
        tail(active(X)) -> tail(X)
        sel(mark(X1), X2) -> sel(X1, X2)
        sel(X1, mark(X2)) -> sel(X1, X2)
        sel(active(X1), X2) -> sel(X1, X2)
        sel(X1, active(X2)) -> sel(X1, X2)
        afterNth(mark(X1), X2) -> afterNth(X1, X2)
        afterNth(X1, mark(X2)) -> afterNth(X1, X2)
        afterNth(active(X1), X2) -> afterNth(X1, X2)
        afterNth(X1, active(X2)) -> afterNth(X1, X2)
        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)
        
)