let br x y b = if b then x else y
let rec for_all_int a b f = if a >= b then true else f a && for_all_int (a+1) b f
let () =
  let h, w = Scanf.scanf "%d %d" (fun a b -> a, b) in
  let s = Array.init h (fun _ -> Scanf.scanf " %s" (fun x -> x)) in
  for_all_int 0 h (fun x -> for_all_int 0 w (fun y ->
    [1, 0; 0, 1; -1, 0; 0, -1] |> List.exists (fun (dx, dy) ->
      let nx, ny = x + dx, y + dy in
      (0 <= nx) && (nx < h) && (0 <= ny) && (ny < w) && (s.(x).[y] = '.' || s.(nx).[ny] = '#'))))
  |> br "Yes" "No" |> print_endline
