WORST_CASE(?,O(n^1))

Solution:
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  "0" :: [] -(0)-> "A"(0)
  "0" :: [] -(0)-> "A"(2)
  "S" :: ["A"(0)] -(0)-> "A"(0)
  "S" :: ["A"(2)] -(2)-> "A"(2)
  "dbl" :: ["A"(0) x "A"(0)] -(1)-> "A"(0)
  "unsafe" :: ["A"(2)] -(1)-> "A"(0)


Cost Free Signatures:
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Base Constructors:
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