(VAR N X XS Y YS ZS )
(RULES 
        U11(tt) -> U12(splitAt(N, XS))
        U12(pair(YS, ZS)) -> pair(cons(X), ZS)
        and(tt) -> X
        tail(cons(N)) -> XS
        afterNth(N, XS) -> snd(splitAt(N, XS))
        fst(pair(X, Y)) -> X
        head(cons(N)) -> N
        natsFrom(N) -> cons(N)
        sel(N, XS) -> head(afterNth(N, XS))
        snd(pair(X, Y)) -> Y
        splitAt(0, XS) -> pair(nil, XS)
        splitAt(s(N), cons(X)) -> U11(tt)
        take(N, XS) -> fst(splitAt(N, XS))
        
)