Problem:
 a() -> a()
 a() -> g(a())
 a() -> f(f(a(),a()),a())
 f(g(a()),f(a(),a())) -> f(g(a()),f(a(),a()))

Proof:
 Nonconfluence Processor:
  terms: f(f(a(),g(a())),a()) *<- a() ->* g(f(f(f(f(a(),a()),a()),a()),a()))
  Qed