open Printf
open Scanf

let () =
  let h, w = scanf "%d %d " (fun x y -> (x, y)) in
  let ct = Array.make 26 0 in
  let rec loop x =
    if x = 0 then ()
    else
      let s = scanf "%s " (fun y -> y) in
      String.iter (fun c -> let i = Char.code c - 97 in ct.(i) <- ct.(i) + 1) s;
      loop (x - 1)
  in
  let rec check g c =
    if c = 0 then true
    else
      let rec iter i =
        if i = 26 then false
        else if ct.(i) >= g then (ct.(i) <- ct.(i) - g; true)
        else iter (i + 1) in
      if iter 0 then check g (c - 1)
      else false
  in
  loop h;
  (if h mod 2 = 0 && w mod 2 = 0 then
    if check 4 ((h / 2) * (w / 2)) then "Yes"
    else "No"
  else if h mod 2 = 0 then
    if check 4 ((h / 2) * (w / 2)) && check 2 (h / 2) then "Yes"
    else "No"
  else if w mod 2 = 0 then
    if check 4 ((h / 2) * (w / 2)) && check 2 (w / 2) then "Yes"
    else "No"
  else
    if check 4 ((h / 2) * (w / 2)) && check 2 (h / 2) && check 2 (w / 2) then "Yes"
    else "No")
  |> printf "%s\n"
