YES
O(n^2)
TRS:
 {
   average(x, s(s(s(y)))) -> s(average(s(x), y)),
         average(s(x), y) -> average(x, s(y)),
  average(0(), s(s(0()))) -> s(0()),
     average(0(), s(0())) -> 0(),
        average(0(), 0()) -> 0()
 }
 Natural interpretation:
  Strict:
   {
     average(x, s(s(s(y)))) -> s(average(s(x), y)),
           average(s(x), y) -> average(x, s(y)),
    average(0(), s(s(0()))) -> s(0()),
       average(0(), s(0())) -> 0(),
          average(0(), 0()) -> 0()
   }
  Weak:
   {}
  Interpretation class: deltarestricted
  [0](delta) = + 0 + 0*delta
  [s](delta, X0) = + 1*X0 + 1 + 0*X0*delta + 3*delta
  [average](delta, X1, X0) = + 1*X0 + 1*X1 + 0 + 0*X0*delta + 2*X1*delta + 1*delta
  
  s_tau_1(delta) = delta/(1 + 0 * delta)
  average_tau_1(delta) = delta/(1 + 2 * delta)average_tau_2(delta) = delta/(1 + 0 * delta)
  
  Qed