YES(?,O(n^1))

Problem:
 f(s(X),X) -> f(X,a(X))
 f(X,c(X)) -> f(s(X),X)
 f(X,X) -> c(X)

Proof:
 Matrix Interpretation Processor:
  dimension: 1
  interpretation:
   [c](x0) = x0 + 8,
   
   [a](x0) = x0 + 1,
   
   [f](x0, x1) = x0 + x1 + 31,
   
   [s](x0) = x0 + 2
  orientation:
   f(s(X),X) = 2X + 33 >= 2X + 32 = f(X,a(X))
   
   f(X,c(X)) = 2X + 39 >= 2X + 33 = f(s(X),X)
   
   f(X,X) = 2X + 31 >= X + 8 = c(X)
  problem:
   
  Qed