WORST_CASE(?,O(n^2))

Solution:
---------

  @ :: [b(1, 0) x b(0, 0)] -(1)-> b(0, 0)
  dd :: [a(0, 0) x b(1, 0)] -(1)-> b(1, 0)
  dd :: [a(0, 0) x b(5, 2)] -(3)-> b(3, 2)
  dd :: [a(0, 0) x b(0, 0)] -(0)-> b(0, 0)
  nil :: [] -(0)-> b(1, 0)
  nil :: [] -(0)-> b(3, 2)
  nil :: [] -(0)-> b(0, 0)
  rev :: [b(3, 2)] -(1)-> b(0, 0)


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

  @ :: [b_cf(0, 0) x b_cf(0, 0)] -(0)-> b_cf(0, 0)
  @ :: [b_cf(1, 0) x b_cf(1, 1)] -(1)-> b_cf(1, 0)
  dd :: [a_cf(0, 0) x b_cf(0, 0)] -(0)-> b_cf(0, 0)
  dd :: [a_cf(0, 0) x b_cf(2, 0)] -(2)-> b_cf(2, 0)
  dd :: [a_cf(0, 0) x b_cf(1, 0)] -(1)-> b_cf(1, 0)
  dd :: [a_cf(0, 0) x b_cf(2, 1)] -(1)-> b_cf(1, 1)
  nil :: [] -(0)-> b_cf(0, 0)
  nil :: [] -(0)-> b_cf(2, 0)
  nil :: [] -(0)-> b_cf(1, 1)
  nil :: [] -(0)-> b_cf(1, 0)
  nil :: [] -(0)-> b_cf(2, 1)
  rev :: [b_cf(2, 0)] -(1)-> b_cf(1, 0)