/* -*- coding: utf-8 -*-
 *
 * 2641.cc:  No.2641 draw X - yukicoder
 */

#include<cstdio>
#include<vector>
#include<algorithm>
 
using namespace std;

/* constant */

const int MAX_HW = 1000000;

/* typedef */

typedef vector<int> vi;
typedef vector<vi> vvi;

/* global variables */

char s[MAX_HW + 4], t[MAX_HW + 4];

/* subroutines */

/* main */

int main() {
  int h, w;
  scanf("%d%d", &h, &w);
  int hw = h * w;
  for (int i = 0; i < h; i++) scanf("%s", s + i * w);

  int m = h + w - 1;
  vvi ls0(m, vi(w, -1)), rs0(m, vi(w, -1));
  vvi ls1(m, vi(w, -1)), rs1(m, vi(w, -1));

  for (int i = 0; i < m; i++) {
    int x0 = max(0, i - (h - 1)), x1 = min(w - 1, i) + 1;

    // y + x = i -> y = i - x
    for (int r = x0; r < x1;) {
      while (r < x1 && s[(i - r) * w + r] == '.') r++;
      if (r >= x1) break;
      int l = r;
      while (r < x1 && s[(i - r) * w + r] == '#') r++;
      for (int x = l; x < r; x++)
	ls0[i][x] = l, rs0[i][x] = r - 1;
    }

    // (h - 1 - y) + x = i -> y = (h - 1) - (i - x)
    for (int r = x0; r < x1;) {
      while (r < x1 && s[(h - 1 - (i - r)) * w + r] == '.') r++;
      if (r >= x1) break;
      int l = r;
      while (r < x1 && s[(h - 1 - (i - r)) * w + r] == '#') r++;
      for (int x = l; x < r; x++)
	ls1[i][x] = l, rs1[i][x] = r - 1;
    }
  }
  
  vvi cs0(m, vi(w + 1, 0)), cs1(m, vi(w + 1, 0));
  for (int y = 1; y < h - 1; y++)
    for (int x = 1; x < w - 1; x++)
      if (s[y * w + x] == '#') {
	int i0 = y + x, i1 = (h - 1 - y) + x;
	int r =
	  min(min(x - ls0[i0][x], rs0[i0][x] - x),
	      min(x - ls1[i1][x], rs1[i1][x] - x));
	if (r > 0) {
	  cs0[i0][x - r]++, cs0[i0][x + r + 1]--;
	  cs1[i1][x - r]++, cs1[i1][x + r + 1]--;
	}
      }

  fill(t, t + hw, '.');
  for (int i = 0; i < m; i++) {
    for (int x = 0; x < w; x++) {
      if (cs0[i][x] > 0) t[(i - x) * w + x] = '#';
      cs0[i][x + 1] += cs0[i][x];
    }
    for (int x = 0; x < w; x++) {
      if (cs1[i][x] > 0) t[(h - 1 - (i - x)) * w + x] = '#';
      cs1[i][x + 1] += cs1[i][x];
    }
  }

  for (int i = 0; i < hw; i++)
    if (s[i] != t[i]) { puts("No"); return 0; }

  puts("Yes");
  return 0;
}