YES
* Step 1: Looptree YES
    + Considered Problem:
        Rules:
          0. start(A,B) -> merge(A,B)      True               (1,1)
          1. merge(A,B) -> merge(A,-1 + B) [A >= 1 && B >= 1] (?,1)
          2. merge(A,B) -> merge(-1 + A,B) [A >= 1 && B >= 1] (?,1)
        Signature:
          {(merge,2);(start,2)}
        Flow Graph:
          [0->{1,2},1->{1,2},2->{1,2}]
        
    + Applied Processor:
        Looptree
    + Details:
        We construct a looptree:
          P: [0,1,2]
          |
          `- p:[1,2] c: [2]
             |
             `- p:[1] c: [1]

YES