WORST_CASE(?,O(n^1))

Solution:
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  "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)
  "main" :: ["L"(1)] -(2)-> "L"(0)
  "nil" :: [] -(0)-> "L"(1)
  "nil" :: [] -(0)-> "L"(0)


Cost Free Signatures:
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