TRS:
 {              from(X) -> cons(X, n__from(s(X))),
   sel(0(), cons(X, Y)) -> X,
  sel(s(X), cons(Y, Z)) -> sel(X, activate(Z)),
                from(X) -> n__from(X),
   activate(n__from(X)) -> from(X),
            activate(X) -> X}
 Fail