let [| H; W |] = stdin.ReadLine().Split(' ') |> Array.map int
let S = [| for i in 1 .. H do
            let s = stdin.ReadLine().Trim()
            yield [| for j in 0 .. s.Length - 1 -> if s.[j] = '#' then 1 else 0 |] |]

let move h w moveh movew (ss:int[][]) = 
    if h+moveh < H && w+movew < W && ss.[h].[w] = 1 && ss.[h+moveh].[w+movew] = 1 then
        [| for hi in 0 .. H - 1 ->
            [| for wi in 0 .. W - 1 do
                if hi = h && wi = w then yield 0
                else if hi = h+moveh && wi = w+movew then yield 0
                else yield ss.[hi].[wi] |] |] |> Some
    else None

let isAll0 (ss:int[][]) =
    0 = Array.fold (fun acc sss -> acc + Array.sum sss) 0 ss

if isAll0 S then printfn "NO"
else
    let result = [ for moveh in 0 .. H - 1 do
        for movew in 0 .. W - 1 do
            if moveh > 0 || movew > 0 then
                let mutable ss = S
                for h in 0 .. H - 1 do
                    for w in 0 .. W - 1 do
                        match (move h w moveh movew ss) with
                        | Some (newss) -> ss <- newss
                        | None -> ()
                if isAll0 ss then yield 1 ]
    if List.sum result > 0 then printfn "YES" else printfn "NO"