Problem:
 f(n__a(),X,X) -> f(activate(X),b(),n__b())
 b() -> a()
 a() -> n__a()
 b() -> n__b()
 activate(n__a()) -> a()
 activate(n__b()) -> b()
 activate(X) -> X

Proof:
 Matrix Interpretation Processor: dim=3
  
  interpretation:
         [0]
   [a] = [0]
         [1],
   
            [0]
   [n__b] = [0]
            [0],
   
         [0]
   [b] = [0]
         [1],
   
                    [1 0 1]     [0]
   [activate](x0) = [0 1 0]x0 + [0]
                    [0 0 1]     [1],
   
                     [1 0 0]     [1 0 0]     [1 1 1]  
   [f](x0, x1, x2) = [0 0 0]x0 + [1 0 0]x1 + [1 0 0]x2
                     [0 0 0]     [1 1 0]     [1 0 0]  ,
   
            [0]
   [n__a] = [0]
            [1]
  orientation:
                   [2 1 1]     [1 0 1]                             
   f(n__a(),X,X) = [2 0 0]X >= [0 0 0]X = f(activate(X),b(),n__b())
                   [2 1 0]     [0 0 0]                             
   
         [0]    [0]      
   b() = [0] >= [0] = a()
         [1]    [1]      
   
         [0]    [0]         
   a() = [0] >= [0] = n__a()
         [1]    [1]         
   
         [0]    [0]         
   b() = [0] >= [0] = n__b()
         [1]    [0]         
   
                      [1]    [0]      
   activate(n__a()) = [0] >= [0] = a()
                      [2]    [1]      
   
                      [0]    [0]      
   activate(n__b()) = [0] >= [0] = b()
                      [1]    [1]      
   
                 [1 0 1]    [0]         
   activate(X) = [0 1 0]X + [0] >= X = X
                 [0 0 1]    [1]         
  problem:
   f(n__a(),X,X) -> f(activate(X),b(),n__b())
   b() -> a()
   a() -> n__a()
   b() -> n__b()
   activate(n__b()) -> b()
   activate(X) -> X
  Unfolding Processor:
   loop length: 5
   terms:
    f(n__a(),n__b(),n__b())
    f(activate(n__b()),b(),n__b())
    f(b(),b(),n__b())
    f(a(),b(),n__b())
    f(n__a(),b(),n__b())
   context: []
   substitution:
    
   Qed