WORST_CASE(?,O(n^2))

Solution:
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  "@" :: ["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"(6, 3)] -(3)-> "b"(3, 3)
  "dd" :: ["a"(0, 0) x "b"(0, 0)] -(0)-> "b"(0, 0)
  "nil" :: [] -(0)-> "b"(1, 0)
  "nil" :: [] -(0)-> "b"(3, 3)
  "nil" :: [] -(0)-> "b"(0, 0)
  "rev" :: ["b"(3, 3)] -(1)-> "b"(0, 0)


Cost Free Signatures:
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  "@" :: ["b"_cf(0, 0) x "b"_cf(0, 0)] -(0)-> "b"_cf(0, 0)
  "@" :: ["b"_cf(1, 0) x "b"_cf(1, 0)] -(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(3, 0)] -(3)-> "b"_cf(3, 0)
  "dd" :: ["a"_cf(0, 0) x "b"_cf(1, 0)] -(1)-> "b"_cf(1, 0)
  "nil" :: [] -(0)-> "b"_cf(0, 0)
  "nil" :: [] -(0)-> "b"_cf(3, 0)
  "nil" :: [] -(0)-> "b"_cf(1, 1)
  "nil" :: [] -(0)-> "b"_cf(1, 0)
  "rev" :: ["b"_cf(3, 0)] -(1)-> "b"_cf(1, 0)


Base Constructors:
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