WORST_CASE(?,O(n^1))

Solution:
---------

  0 :: [] -(0)-> Nat(1)
  add :: [Nat(1) x Nat(0)] -(1)-> Nat(0)
  s :: [Nat(1)] -(1)-> Nat(1)
  s :: [Nat(0)] -(0)-> Nat(0)


Cost Free Signatures:
---------------------

  0 :: [] -(0)-> Nat_cf(0)
  add :: [Nat_cf(0) x Nat_cf(0)] -(0)-> Nat_cf(0)
  s :: [Nat_cf(0)] -(0)-> Nat_cf(0)