WORST_CASE(?,O(n^1))
* Step 1: Ara WORST_CASE(?,O(n^1))
    + Considered Problem:
        - Strict TRS:
            ackin(s(X),s(Y)) -> u21(ackin(s(X),Y),X)
            u21(ackout(X),Y) -> u22(ackin(Y,X))
        - Signature:
            {ackin/2,u21/2} / {ackout/1,s/1,u22/1}
        - Obligation:
            innermost runtime complexity wrt. defined symbols {ackin,u21} and constructors {ackout,s,u22}
    + Applied Processor:
        Ara {heuristics_ = NoHeuristics, minDegree = 1, maxDegree = 3, araTimeout = 60, araFindStrictRules = Nothing, araSmtSolver = Z3}
    + Details:
        Signatures used:
        ----------------
          ackin :: [A(0) x A(6)] -(9)-> A(6)
          ackout :: [A(6)] -(6)-> A(6)
          s :: [A(0)] -(0)-> A(0)
          s :: [A(6)] -(6)-> A(6)
          u21 :: [A(6) x A(0)] -(4)-> A(6)
          u22 :: [A(0)] -(0)-> A(13)
        
        
        Cost-free Signatures used:
        --------------------------
          ackin :: [A_cf(0) x A_cf(0)] -(0)-> A_cf(0)
          ackout :: [A_cf(0)] -(0)-> A_cf(0)
          s :: [A_cf(0)] -(0)-> A_cf(0)
          u21 :: [A_cf(0) x A_cf(0)] -(0)-> A_cf(0)
          u22 :: [A_cf(0)] -(0)-> A_cf(0)
        
        
        Base Constructor Signatures used:
        ---------------------------------
          ackout_A :: [A(1)] -(1)-> A(1)
          s_A :: [A(1)] -(1)-> A(1)
          u22_A :: [A(0)] -(0)-> A(1)
        
* Step 2: Open MAYBE
    - Strict TRS:
        ackin(s(X),s(Y)) -> u21(ackin(s(X),Y),X)
        u21(ackout(X),Y) -> u22(ackin(Y,X))
    - Signature:
        {ackin/2,u21/2} / {ackout/1,s/1,u22/1}
    - Obligation:
        innermost runtime complexity wrt. defined symbols {ackin,u21} and constructors {ackout,s,u22}
Following problems could not be solved:
  - Strict TRS:
      ackin(s(X),s(Y)) -> u21(ackin(s(X),Y),X)
      u21(ackout(X),Y) -> u22(ackin(Y,X))
  - Signature:
      {ackin/2,u21/2} / {ackout/1,s/1,u22/1}
  - Obligation:
      innermost runtime complexity wrt. defined symbols {ackin,u21} and constructors {ackout,s,u22}
WORST_CASE(?,O(n^1))