YES
O(n^2)
TRS:
 {
        fst(0(), Z) -> nil(),
  fst(s(), cons(Y)) -> cons(Y),
            from(X) -> cons(X),
        add(0(), X) -> X,
        add(s(), Y) -> s(),
         len(nil()) -> 0(),
       len(cons(X)) -> s()
 }
 DUP: We consider a non-duplicating system.
  Trs:
   {
          fst(0(), Z) -> nil(),
    fst(s(), cons(Y)) -> cons(Y),
              from(X) -> cons(X),
          add(0(), X) -> X,
          add(s(), Y) -> s(),
           len(nil()) -> 0(),
         len(cons(X)) -> s()
   }
  Matrix Interpretation:
   Interpretation class: triangular
         [X1]    [1 1][X1]   [1]
   [len]([X0]) = [0 1][X0] + [1]
   
         [X3]  [X1]    [1 1][X3]   [1 0][X1]   [1]
   [add]([X2], [X0]) = [0 1][X2] + [0 1][X0] + [1]
   
          [X1]    [1 0][X1]   [1]
   [from]([X0]) = [0 0][X0] + [1]
   
         [0]
   [s] = [1]
   
          [X1]    [1 0][X1]   [0]
   [cons]([X0]) = [0 0][X0] + [1]
   
         [1]
   [0] = [1]
   
         [X3]  [X1]    [1 1][X3]   [1 1][X1]   [0]
   [fst]([X2], [X0]) = [0 1][X2] + [0 1][X0] + [1]
   
           [0]
   [nil] = [1]
   
   
   Qed