MAYBE

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

Proof:
 DP Processor:
  DPs:
   f#(f(a(),x),a()) -> f#(a(),a())
   f#(f(a(),x),a()) -> f#(x,a())
   f#(f(a(),x),a()) -> f#(f(x,a()),f(a(),a()))
   f#(f(a(),x),a()) -> f#(f(f(x,a()),f(a(),a())),a())
  TRS:
   f(f(a(),x),a()) -> f(f(f(x,a()),f(a(),a())),a())
  Open