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