TRS:
 {f(s(X), X) -> f(X, a(X)),
  f(X, c(X)) -> f(s(X), X),
     f(X, X) -> c(X)}
 MPO:
  Prec:
   s > a, 
   f ~ c > s
   empty
  Strict:
   {}
   Weak:
    {}
  Qed