Problem:
 a() -> a()
 f(b(),x) -> b()
 f(x,a()) -> a()

Proof:
 Nonconfluence Processor:
  terms: a() *<- f(b(),a()) ->* b()
  Qed
  
  first automaton:
   final states: {1}
   transitions:
    a() -> 1*
  
  second automaton:
   final states: {2}
   transitions:
    b() -> 2*