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

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