let () = Scanf.scanf "%d %d\n" @@ fun h w ->
  let ss = Array.init h @@ fun _ -> Scanf.scanf "%s\n" @@ fun s -> s in
  Array.init h (fun i -> 
    Array.to_list @@ Array.init w (fun j -> (i, j)))
  |> Array.to_list
  |> List.concat
  |> List.for_all (fun (i, j) ->
      ss.(i).[j] = '.' || 
        List.exists (fun (i, j) ->
          try ss.(i).[j] = '#' with _ -> false)
        [(i + 1, j); (i - 1, j); (i, j + 1); (i, j - 1) ])
  |> function
    | true -> print_endline "Yes"
    | false -> print_endline "No"