WORST_CASE(?,O(n^2))

Solution:
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  "append" :: ["b"(2, 0) x "b"(0, 0)] -(1)-> "b"(0, 0)
  "attach" :: ["a"(0, 0) x "b"(3, 0)] -(1)-> "b"(2, 0)
  "cons" :: ["a"(0, 0) x "b"(2, 0)] -(2)-> "b"(2, 0)
  "cons" :: ["a"(0, 0) x "b"(3, 0)] -(3)-> "b"(3, 0)
  "cons" :: ["a"(0, 0) x "b"(6, 3)] -(3)-> "b"(3, 3)
  "cons" :: ["a"(0, 0) x "b"(0, 0)] -(0)-> "b"(0, 0)
  "nil" :: [] -(0)-> "b"(2, 0)
  "nil" :: [] -(0)-> "b"(3, 0)
  "nil" :: [] -(0)-> "b"(3, 3)
  "nil" :: [] -(0)-> "b"(0, 0)
  "pair" :: ["a"(0, 0) x "a"(0, 0)] -(0)-> "a"(0, 0)
  "pairs" :: ["b"(3, 3)] -(1)-> "b"(0, 0)


Cost Free Signatures:
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  "append" :: ["b"_cf(0, 0) x "b"_cf(0, 0)] -(1)-> "b"_cf(0, 0)
  "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)] -(0)-> "b"_cf(0, 0)
  "cons" :: ["a"_cf(0, 0) x "b"_cf(0, 0)] -(0)-> "b"_cf(0, 0)
  "nil" :: [] -(0)-> "b"_cf(0, 0)
  "pair" :: ["a"_cf(0, 0) x "a"_cf(0, 0)] -(0)-> "a"_cf(0, 0)
  "pairs" :: ["b"_cf(0, 0)] -(0)-> "b"_cf(0, 0)


Base Constructors:
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