using System;
using System.Collections.Generic;
using System.Linq;

class Magatro
{
    static int H, W;
    static string[] S;
    static void Main()
    {
        Read();
        
       for(int x = -W; x <= W; x++)
        {
            for(int y = 0; y <= H; y++)
            {
                if (x == 0 && y == 0)
                {
                    continue;
                }
                if (s(x, y))
                {
                    Console.WriteLine("YES");
                    return;
                }
                
            }
        }
        Console.WriteLine("NO");
    }
    static bool s(int x,int y)
    {
        int[,] ban = new int[H, W];
        for(int i = 0; i < H; i++)
        {
            for(int j = 0; j < W; j++)
            {
                if (S[i][j] == '#')
                {
                    if (ban[i, j] == 0)
                    {
                        ban[i, j] = 1;
                        int bly = i + y;
                        int blx = j + x;
                      
                        if (blx < W && blx >= 0 && bly < H && bly >= 0)
                        {
                            if (S[bly][blx] != '#')
                            {
                                return false;
                            }
                            ban[bly, blx] = 2;
                        }
                        else
                        {
                            return false;
                        }
                    }
                }
            }
        }
        bool a = false;
        for (int i = 0; i < H; i++)
        {
            for (int j = 0; j < W; j++)
            {
                if (S[i][j] == '#' )
                {
                    a = true;
                    if( ban[i, j] == 0)
                    return false;
                }
               
            }
        }
                return a;
    }
    static void Read()
    {

        string[] s = Console.ReadLine().Split(' ');
        H = int.Parse(s[0]);
        W = int.Parse(s[1]);
        S = new string[H];
        for(int i = 0; i < H; i++)
        {
            S[i] = Console.ReadLine();
        }
    }
   
}