MAYBE
* Step 1: UnsatPaths MAYBE
    + Considered Problem:
        Rules:
          0. f0(A,B,C,D) -> f6(B,B,D,D)           True                  (1,1)
          1. f6(A,B,C,D) -> f6(-1 + A,B,-1 + C,D) [0 >= 1 + A]          (?,1)
          2. f6(A,B,C,D) -> f6(-1 + A,B,-1 + C,D) [A >= 1]              (?,1)
          3. f6(A,B,C,D) -> f14(0,B,C,D)          [D >= 1 + B && A = 0] (?,1)
          4. f6(A,B,C,D) -> f14(0,B,C,D)          [B >= 1 + D && A = 0] (?,1)
          5. f6(A,B,C,D) -> f14(0,B,C,B)          [A = 0 && B = D]      (?,1)
        Signature:
          {(f0,4);(f14,4);(f6,4)}
        Flow Graph:
          [0->{1,2,3,4,5},1->{1,2,3,4,5},2->{1,2,3,4,5},3->{},4->{},5->{}]
        
    + Applied Processor:
        UnsatPaths
    + Details:
        We remove following edges from the transition graph: [(1,2),(1,3),(1,4),(1,5),(2,1)]
* Step 2: FromIts MAYBE
    + Considered Problem:
        Rules:
          0. f0(A,B,C,D) -> f6(B,B,D,D)           True                  (1,1)
          1. f6(A,B,C,D) -> f6(-1 + A,B,-1 + C,D) [0 >= 1 + A]          (?,1)
          2. f6(A,B,C,D) -> f6(-1 + A,B,-1 + C,D) [A >= 1]              (?,1)
          3. f6(A,B,C,D) -> f14(0,B,C,D)          [D >= 1 + B && A = 0] (?,1)
          4. f6(A,B,C,D) -> f14(0,B,C,D)          [B >= 1 + D && A = 0] (?,1)
          5. f6(A,B,C,D) -> f14(0,B,C,B)          [A = 0 && B = D]      (?,1)
        Signature:
          {(f0,4);(f14,4);(f6,4)}
        Flow Graph:
          [0->{1,2,3,4,5},1->{1},2->{2,3,4,5},3->{},4->{},5->{}]
        
    + Applied Processor:
        FromIts
    + Details:
        ()
* Step 3: Unfold MAYBE
    + Considered Problem:
        Rules:
          f0(A,B,C,D) -> f6(B,B,D,D)            True
          f6(A,B,C,D) -> f6(-1 + A,B,-1 + C,D)  [0 >= 1 + A]
          f6(A,B,C,D) -> f6(-1 + A,B,-1 + C,D)  [A >= 1]
          f6(A,B,C,D) -> f14(0,B,C,D)           [D >= 1 + B && A = 0]
          f6(A,B,C,D) -> f14(0,B,C,D)           [B >= 1 + D && A = 0]
          f6(A,B,C,D) -> f14(0,B,C,B)           [A = 0 && B = D]
        Signature:
          {(f0,4);(f14,4);(f6,4)}
        Rule Graph:
          [0->{1,2,3,4,5},1->{1},2->{2,3,4,5},3->{},4->{},5->{}]
    + Applied Processor:
        Unfold
    + Details:
        ()
* Step 4: AddSinks MAYBE
    + Considered Problem:
        Rules:
          f0.0(A,B,C,D) -> f6.1(B,B,D,D)            True
          f0.0(A,B,C,D) -> f6.2(B,B,D,D)            True
          f0.0(A,B,C,D) -> f6.3(B,B,D,D)            True
          f0.0(A,B,C,D) -> f6.4(B,B,D,D)            True
          f0.0(A,B,C,D) -> f6.5(B,B,D,D)            True
          f6.1(A,B,C,D) -> f6.1(-1 + A,B,-1 + C,D)  [0 >= 1 + A]
          f6.2(A,B,C,D) -> f6.2(-1 + A,B,-1 + C,D)  [A >= 1]
          f6.2(A,B,C,D) -> f6.3(-1 + A,B,-1 + C,D)  [A >= 1]
          f6.2(A,B,C,D) -> f6.4(-1 + A,B,-1 + C,D)  [A >= 1]
          f6.2(A,B,C,D) -> f6.5(-1 + A,B,-1 + C,D)  [A >= 1]
          f6.3(A,B,C,D) -> f14.6(0,B,C,D)           [D >= 1 + B && A = 0]
          f6.4(A,B,C,D) -> f14.6(0,B,C,D)           [B >= 1 + D && A = 0]
          f6.5(A,B,C,D) -> f14.6(0,B,C,B)           [A = 0 && B = D]
        Signature:
          {(f0.0,4);(f14.6,4);(f6.1,4);(f6.2,4);(f6.3,4);(f6.4,4);(f6.5,4)}
        Rule Graph:
          [0->{5},1->{6,7,8,9},2->{10},3->{11},4->{12},5->{5},6->{6,7,8,9},7->{10},8->{11},9->{12},10->{},11->{}
          ,12->{}]
    + Applied Processor:
        AddSinks
    + Details:
        ()
* Step 5: Failure MAYBE
  + Considered Problem:
      Rules:
        f0.0(A,B,C,D)  -> f6.1(B,B,D,D)            True
        f0.0(A,B,C,D)  -> f6.2(B,B,D,D)            True
        f0.0(A,B,C,D)  -> f6.3(B,B,D,D)            True
        f0.0(A,B,C,D)  -> f6.4(B,B,D,D)            True
        f0.0(A,B,C,D)  -> f6.5(B,B,D,D)            True
        f6.1(A,B,C,D)  -> f6.1(-1 + A,B,-1 + C,D)  [0 >= 1 + A]
        f6.2(A,B,C,D)  -> f6.2(-1 + A,B,-1 + C,D)  [A >= 1]
        f6.2(A,B,C,D)  -> f6.3(-1 + A,B,-1 + C,D)  [A >= 1]
        f6.2(A,B,C,D)  -> f6.4(-1 + A,B,-1 + C,D)  [A >= 1]
        f6.2(A,B,C,D)  -> f6.5(-1 + A,B,-1 + C,D)  [A >= 1]
        f6.3(A,B,C,D)  -> f14.6(0,B,C,D)           [D >= 1 + B && A = 0]
        f6.4(A,B,C,D)  -> f14.6(0,B,C,D)           [B >= 1 + D && A = 0]
        f6.5(A,B,C,D)  -> f14.6(0,B,C,B)           [A = 0 && B = D]
        f14.6(A,B,C,D) -> exitus616(A,B,C,D)       True
        f14.6(A,B,C,D) -> exitus616(A,B,C,D)       True
        f14.6(A,B,C,D) -> exitus616(A,B,C,D)       True
        f14.6(A,B,C,D) -> exitus616(A,B,C,D)       True
        f14.6(A,B,C,D) -> exitus616(A,B,C,D)       True
        f14.6(A,B,C,D) -> exitus616(A,B,C,D)       True
        f6.1(A,B,C,D)  -> exitus616(A,B,C,D)       True
      Signature:
        {(exitus616,4);(f0.0,4);(f14.6,4);(f6.1,4);(f6.2,4);(f6.3,4);(f6.4,4);(f6.5,4)}
      Rule Graph:
        [0->{5},1->{6,7,8,9},2->{10},3->{11},4->{12},5->{5,19},6->{6,7,8,9},7->{10},8->{11},9->{12},10->{15,18}
        ,11->{14,17},12->{13,16}]
  + Applied Processor:
      Decompose Greedy
  + Details:
      We construct a looptree:
        P: [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19]
        |
        +- p:[6] c: [6]
        |
        `- p:[5] c: []
MAYBE