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