WORST_CASE(?,O(n^1))

Solution:
---------

  append :: [L(1) x L(0)] -(1)-> L(0)
  cons :: [Elem(0) x L(1)] -(1)-> L(1)
  cons :: [Elem(0) x L(0)] -(0)-> L(0)
  nil :: [] -(0)-> L(1)


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

  append :: [L_cf(0) x L_cf(0)] -(0)-> L_cf(0)
  cons :: [Elem_cf(0) x L_cf(0)] -(0)-> L_cf(0)
  nil :: [] -(0)-> L_cf(0)