MAYBE
* Step 1: UnreachableRules MAYBE
    + Considered Problem:
        Rules:
          0. f9(A,B,C,D)  -> f15(A,0,E,D) [0 >= A && E >= 1] (?,1)
          1. f15(A,B,C,D) -> f15(A,B,C,D) [C >= 1]           (?,1)
          2. f23(A,B,C,D) -> f23(A,B,C,D) True               (?,1)
          3. f25(A,B,C,D) -> f28(A,B,C,D) True               (?,1)
          4. f15(A,B,C,D) -> f9(E,B,C,0)  [0 >= C]           (?,1)
          5. f9(A,B,C,D)  -> f23(A,B,C,D) [A >= 1]           (?,1)
          6. f0(A,B,C,D)  -> f9(E,0,C,0)  True               (1,1)
        Signature:
          {(f0,4);(f15,4);(f23,4);(f25,4);(f28,4);(f9,4)}
        Flow Graph:
          [0->{1,4},1->{1,4},2->{2},3->{},4->{0,5},5->{2},6->{0,5}]
        
    + Applied Processor:
        UnreachableRules
    + Details:
        Following transitions are not reachable from the starting states and are revomed: [3]
* Step 2: UnsatPaths MAYBE
    + Considered Problem:
        Rules:
          0. f9(A,B,C,D)  -> f15(A,0,E,D) [0 >= A && E >= 1] (?,1)
          1. f15(A,B,C,D) -> f15(A,B,C,D) [C >= 1]           (?,1)
          2. f23(A,B,C,D) -> f23(A,B,C,D) True               (?,1)
          4. f15(A,B,C,D) -> f9(E,B,C,0)  [0 >= C]           (?,1)
          5. f9(A,B,C,D)  -> f23(A,B,C,D) [A >= 1]           (?,1)
          6. f0(A,B,C,D)  -> f9(E,0,C,0)  True               (1,1)
        Signature:
          {(f0,4);(f15,4);(f23,4);(f25,4);(f28,4);(f9,4)}
        Flow Graph:
          [0->{1,4},1->{1,4},2->{2},4->{0,5},5->{2},6->{0,5}]
        
    + Applied Processor:
        UnsatPaths
    + Details:
        We remove following edges from the transition graph: [(0,4),(1,4)]
* Step 3: FromIts MAYBE
    + Considered Problem:
        Rules:
          0. f9(A,B,C,D)  -> f15(A,0,E,D) [0 >= A && E >= 1] (?,1)
          1. f15(A,B,C,D) -> f15(A,B,C,D) [C >= 1]           (?,1)
          2. f23(A,B,C,D) -> f23(A,B,C,D) True               (?,1)
          4. f15(A,B,C,D) -> f9(E,B,C,0)  [0 >= C]           (?,1)
          5. f9(A,B,C,D)  -> f23(A,B,C,D) [A >= 1]           (?,1)
          6. f0(A,B,C,D)  -> f9(E,0,C,0)  True               (1,1)
        Signature:
          {(f0,4);(f15,4);(f23,4);(f25,4);(f28,4);(f9,4)}
        Flow Graph:
          [0->{1},1->{1},2->{2},4->{0,5},5->{2},6->{0,5}]
        
    + Applied Processor:
        FromIts
    + Details:
        ()
* Step 4: Unfold MAYBE
    + Considered Problem:
        Rules:
          f9(A,B,C,D)  -> f15(A,0,E,D)  [0 >= A && E >= 1]
          f15(A,B,C,D) -> f15(A,B,C,D)  [C >= 1]
          f23(A,B,C,D) -> f23(A,B,C,D)  True
          f15(A,B,C,D) -> f9(E,B,C,0)   [0 >= C]
          f9(A,B,C,D)  -> f23(A,B,C,D)  [A >= 1]
          f0(A,B,C,D)  -> f9(E,0,C,0)   True
        Signature:
          {(f0,4);(f15,4);(f23,4);(f25,4);(f28,4);(f9,4)}
        Rule Graph:
          [0->{1},1->{1},2->{2},4->{0,5},5->{2},6->{0,5}]
    + Applied Processor:
        Unfold
    + Details:
        ()
* Step 5: AddSinks MAYBE
    + Considered Problem:
        Rules:
          f9.0(A,B,C,D)  -> f15.1(A,0,E,D)  [0 >= A && E >= 1]
          f15.1(A,B,C,D) -> f15.1(A,B,C,D)  [C >= 1]
          f23.2(A,B,C,D) -> f23.2(A,B,C,D)  True
          f15.4(A,B,C,D) -> f9.0(E,B,C,0)   [0 >= C]
          f15.4(A,B,C,D) -> f9.5(E,B,C,0)   [0 >= C]
          f9.5(A,B,C,D)  -> f23.2(A,B,C,D)  [A >= 1]
          f0.6(A,B,C,D)  -> f9.0(E,0,C,0)   True
          f0.6(A,B,C,D)  -> f9.5(E,0,C,0)   True
        Signature:
          {(f0.6,4);(f15.1,4);(f15.4,4);(f23.2,4);(f9.0,4);(f9.5,4)}
        Rule Graph:
          [0->{1},1->{1},2->{2},3->{0},4->{5},5->{2},6->{0},7->{5}]
    + Applied Processor:
        AddSinks
    + Details:
        ()
* Step 6: Failure MAYBE
  + Considered Problem:
      Rules:
        f9.0(A,B,C,D)  -> f15.1(A,0,E,D)      [0 >= A && E >= 1]
        f15.1(A,B,C,D) -> f15.1(A,B,C,D)      [C >= 1]
        f23.2(A,B,C,D) -> f23.2(A,B,C,D)      True
        f15.4(A,B,C,D) -> f9.0(E,B,C,0)       [0 >= C]
        f15.4(A,B,C,D) -> f9.5(E,B,C,0)       [0 >= C]
        f9.5(A,B,C,D)  -> f23.2(A,B,C,D)      [A >= 1]
        f0.6(A,B,C,D)  -> f9.0(E,0,C,0)       True
        f0.6(A,B,C,D)  -> f9.5(E,0,C,0)       True
        f23.2(A,B,C,D) -> exitus616(A,B,C,D)  True
        f15.1(A,B,C,D) -> exitus616(A,B,C,D)  True
        f23.2(A,B,C,D) -> exitus616(A,B,C,D)  True
        f15.1(A,B,C,D) -> exitus616(A,B,C,D)  True
      Signature:
        {(exitus616,4);(f0.6,4);(f15.1,4);(f15.4,4);(f23.2,4);(f9.0,4);(f9.5,4)}
      Rule Graph:
        [0->{1},1->{1,9,11},2->{2,8,10},3->{0},4->{5},5->{2},6->{0},7->{5}]
  + Applied Processor:
      Decompose Greedy
  + Details:
      We construct a looptree:
        P: [0,1,2,3,4,5,6,7,8,9,10,11]
        |
        +- p:[2] c: []
        |
        `- p:[1] c: []
MAYBE