#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
#include <math.h>
#include <limits.h>
#define Max(a, b) ((a) > (b) ? (a) : (b))
#define Min(a, b) ((a) > (b) ? (b) : (a))
#define abs(x) ((x) > 0 ? (x) : -(x))
#define rep(i, n) for(int i = 0; i < (n); i++)
#define INF 1000000000000 //10^12
#define MOD 1000000007 //10^9 + 7
#define endl printf("\n")
typedef long long ll;

int
main(int argc, char **argv)
{
  int h, w;
  scanf("%d %d", &h, &w);
  
  char s[50][51];
  for (int i = 0; i < h; i++) {
    scanf("%s", s[i]);
  }
  int b = 0;
  for(int i = 0; i < h; i++) {
    for(int j = 0; j < w; j++) {
      if (s[i][j] == '#') b++;
    }
  }
  if (b == 0 || (b & 1) == 1) {
    printf("NO\n");
    return 0;
  }

  int cnt;
  for (int y = -h + 1; y < h; y++) {
    for (int x = -w + 1; x < w; x++) {
      int v[50][50] = {}; cnt = 0;
      for (int i = 0; i < h; i++) {
	for (int j = 0; j < w; j++) {
	  if(v[i][j] != 1 && s[i][j] == '#' &&
	     i + y < h && j + x < w && i + y >= 0 && j + x >= 0 &&
	     v[i + y][j + x] != 1 && s[i + y][j + x] == '#') {
	    v[i][j]++; v[i + y][j + x]++;
	    cnt += 2;
	  }
	}
      }
      if(b == cnt){
	//printf("%d %d\n", x, y);
	printf("YES\n");
	return 0;
      }
    }
  }

  printf("NO\n");

  return 0;
}