TRS:
 {                   fib(N) -> sel(N, fib1(s(0()), s(0()))),
                 fib1(X, Y) -> cons(X, n__fib1(Y, n__add(X, Y))),
                add(0(), X) -> X,
               add(s(X), Y) -> s(add(X, Y)),
      sel(0(), cons(X, XS)) -> X,
     sel(s(N), cons(X, XS)) -> sel(N, activate(XS)),
               fib1(X1, X2) -> n__fib1(X1, X2),
                add(X1, X2) -> n__add(X1, X2),
  activate(n__fib1(X1, X2)) -> fib1(activate(X1), activate(X2)),
   activate(n__add(X1, X2)) -> add(activate(X1), activate(X2)),
                activate(X) -> X}
 Fail