YES
O(n)
TRS:
 {f(f(a())) -> c()}
 Natural interpretation:
  Strict:
   {f(f(a())) -> c()}
  Weak:
   {}
  Interpretation class: stronglylinear
  [a] = + 0
  [f](X0) = + 1*X0 + 1
  [c] = + 0
  
  Qed