(VAR N X XS Y YS ZS )
(RULES 
        U11(tt, N, XS) -> U12(tt, activate(N), activate(XS))
        U12(tt, N, XS) -> snd(splitAt(activate(N), activate(XS)))
        U21(tt, X) -> U22(tt, activate(X))
        U22(tt, X) -> activate(X)
        U31(tt, N) -> U32(tt, activate(N))
        U32(tt, N) -> activate(N)
        U41(tt, N, XS) -> U42(tt, activate(N), activate(XS))
        U42(tt, N, XS) -> head(afterNth(activate(N), activate(XS)))
        U51(tt, Y) -> U52(tt, activate(Y))
        U52(tt, Y) -> activate(Y)
        U61(tt, N, X, XS) -> U62(tt, activate(N), activate(X), activate(XS))
        U62(tt, N, X, XS) -> U63(tt, activate(N), activate(X), activate(XS))
        U63(tt, N, X, XS) -> U64(splitAt(activate(N), activate(XS)), activate(X))
        U64(pair(YS, ZS), X) -> pair(cons(activate(X), YS), ZS)
        U71(tt, XS) -> U72(tt, activate(XS))
        U72(tt, XS) -> activate(XS)
        U81(tt, N, XS) -> U82(tt, activate(N), activate(XS))
        U82(tt, N, XS) -> fst(splitAt(activate(N), activate(XS)))
        afterNth(N, XS) -> U11(tt, N, XS)
        fst(pair(X, Y)) -> U21(tt, X)
        head(cons(N, XS)) -> U31(tt, N)
        natsFrom(N) -> cons(N, n__natsFrom(s(N)))
        sel(N, XS) -> U41(tt, N, XS)
        snd(pair(X, Y)) -> U51(tt, Y)
        splitAt(0, XS) -> pair(nil, XS)
        splitAt(s(N), cons(X, XS)) -> U61(tt, N, X, activate(XS))
        tail(cons(N, XS)) -> U71(tt, activate(XS))
        take(N, XS) -> U81(tt, N, XS)
        natsFrom(X) -> n__natsFrom(X)
        activate(n__natsFrom(X)) -> natsFrom(X)
        activate(X) -> X
        
)