NO
* Step 1: TrivialSCCs NO
    + Considered Problem:
        Rules:
          0. f6(A,B,C,D) -> f16(A,B,C,D) [1 + A >= B]                 (?,1)
          1. f6(A,B,C,D) -> f6(E,B,C,E)  [B >= 2 + A && C >= E^2]     (?,1)
          2. f6(A,B,C,D) -> f6(A,E,C,E)  [B >= 2 + A && E^2 >= 1 + C] (?,1)
          3. f0(A,B,C,D) -> f6(1,C,C,D)  True                         (1,1)
        Signature:
          {(f0,4);(f16,4);(f6,4)}
        Flow Graph:
          [0->{},1->{0,1,2},2->{0,1,2},3->{0,1,2}]
        
    + Applied Processor:
        TrivialSCCs
    + Details:
        All trivial SCCs of the transition graph admit timebound 1.
* Step 2: Looptree NO
    + Considered Problem:
        Rules:
          0. f6(A,B,C,D) -> f16(A,B,C,D) [1 + A >= B]                 (1,1)
          1. f6(A,B,C,D) -> f6(E,B,C,E)  [B >= 2 + A && C >= E^2]     (?,1)
          2. f6(A,B,C,D) -> f6(A,E,C,E)  [B >= 2 + A && E^2 >= 1 + C] (?,1)
          3. f0(A,B,C,D) -> f6(1,C,C,D)  True                         (1,1)
        Signature:
          {(f0,4);(f16,4);(f6,4)}
        Flow Graph:
          [0->{},1->{0,1,2},2->{0,1,2},3->{0,1,2}]
        
    + Applied Processor:
        Looptree
    + Details:
        We construct a looptree:
          P: [0,1,2,3]
          |
          `- p:[1,2] c: []

NO