TRS:
 {              a__from(X) -> cons(mark(X), from(s(X))),
   a__sel(0(), cons(X, Y)) -> mark(X),
  a__sel(s(X), cons(Y, Z)) -> a__sel(mark(X), mark(Z)),
             mark(from(X)) -> a__from(mark(X)),
         mark(sel(X1, X2)) -> a__sel(mark(X1), mark(X2)),
        mark(cons(X1, X2)) -> cons(mark(X1), X2),
                mark(s(X)) -> s(mark(X)),
                 mark(0()) -> 0(),
                a__from(X) -> from(X),
            a__sel(X1, X2) -> sel(X1, X2)}
 Fail