#include <iostream>
#include <vector>
#include <map>
#include <algorithm>
#include <limits.h>
#include <time.h>
#include <string>
#include <string.h>
#include <sstream>
#include <set>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <stack>
#include <queue>

using namespace std;

typedef long long ll;

int height, width;

const int WHITE = -1;
const int RED = 0;
const int BLUE = 1;

const int MAX_H = 50;
const int MAX_W = 50;

bool isInside(int y, int x){
  return (0 <= y && y < height && 0 <= x && x < width);
}

bool isOutside(int y, int x){
  return (y < 0 || height <= y || x < 0 || width <= x);
}

char field[MAX_H][MAX_W];

bool check(int dy, int dx){
  int color[height][width];
  memset(color, WHITE, sizeof(color));
  bool painted = false;

  for(int y = 0; y < height; y++){
    for(int x = 0; x < width; x++){
      if (field[y][x] == '#' && color[y][x] == -1){
        painted = true;
        color[y][x] = RED;

        int ny = y + dy;
        int nx = x + dx;
        if (isOutside(ny, nx)) return false;
        if (field[ny][nx] == '.' || color[ny][nx] != WHITE) return false;
        color[ny][nx] = BLUE;
      }
    }
  }

  return painted;
}

int main(){
  cin >> height >> width;


  for(int y = 0; y < height; y++){
    for(int x = 0; x < width; x++){
      cin >> field[y][x];
    }
  }

  bool success = false;

  for(int dy = -height; dy < height; dy++){
    for(int dx = -width; dx < width; dx++){
      success |= check(dy, dx);
    }
  }

  if(success){
    cout << "YES" << endl;
  }else{
    cout << "NO" << endl;
  }

  return 0;
}