WORST_CASE(?,O(n^2))

Solution:
---------

  append :: [b(1, 0) x b(0, 0)] -(1)-> b(0, 0)
  attach :: [a(0, 0) x b(10, 0)] -(1)-> b(1, 0)
  cons :: [a(1, 0) x b(1, 0)] -(1)-> b(1, 0)
  cons :: [a(10, 0) x b(10, 0)] -(10)-> b(10, 0)
  cons :: [a(12, 0) x b(12, 12)] -(12)-> b(0, 12)
  cons :: [a(0, 0) x b(0, 0)] -(0)-> b(0, 0)
  nil :: [] -(0)-> b(1, 0)
  nil :: [] -(0)-> b(10, 0)
  nil :: [] -(0)-> b(0, 12)
  nil :: [] -(0)-> b(7, 6)
  pair :: [a(0, 0) x a(0, 0)] -(0)-> a(3, 8)
  pairs :: [b(0, 12)] -(8)-> b(0, 0)


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

  append :: [b_cf(0, 0) x b_cf(0, 0)] -(0)-> b_cf(0, 0)
  attach :: [a_cf(0, 0) x b_cf(0, 0)] -(8)-> b_cf(0, 0)
  attach :: [a_cf(0, 0) x b_cf(0, 0)] -(0)-> b_cf(0, 0)
  cons :: [a_cf(0, 0) x b_cf(0, 0)] -(0)-> b_cf(0, 0)
  cons :: [a_cf(1, 0) x b_cf(1, 0)] -(1)-> b_cf(1, 0)
  nil :: [] -(0)-> b_cf(0, 0)
  nil :: [] -(0)-> b_cf(3, 2)
  nil :: [] -(0)-> b_cf(1, 0)
  pair :: [a_cf(0, 0) x a_cf(0, 0)] -(0)-> a_cf(11, 4)
  pair :: [a_cf(0, 0) x a_cf(0, 0)] -(0)-> a_cf(1, 0)
  pairs :: [b_cf(1, 0)] -(0)-> b_cf(0, 0)


Base Constructors:
------------------
  cons_b :: [a(1, 0) x b(1, 0)] -(1)-> b(1, 0)
  cons_b :: [a(1, 0) x b(1, 1)] -(1)-> b(0, 1)
  nil_b :: [] -(0)-> b(1, 0)
  nil_b :: [] -(0)-> b(0, 1)
  pair_a :: [a(0, 0) x a(0, 0)] -(0)-> a(1, 0)
  pair_a :: [a(0, 0) x a(0, 0)] -(0)-> a(0, 1)