#include <bits/stdc++.h>
using namespace std;
const int INF = 0x3f3f3f3f;
const int MAX = 10e6 + 5;
const int MOD = 10e9 + 7;
char wa[100][100];
int main() {
  ios::sync_with_stdio(false);
  int H, W;
  memset(wa, 0, sizeof(wa));
  cin >> H >> W;
  for (int i = 0; i < H; i++) {
    for (int j = 0; j < W; j++) {
      cin >> wa[i][j];
    }
  }
  int flag = 0;
  for (int i = 1; i < H; i++) {
    for (int j = 1; j < W; j++) {
      if (wa[i][j] == '#') {
        if (wa[i - 1][j] == '#' && wa[i + 1][j] == '#' && wa[i][j - 1] == '#' &&
            wa[i][j + 1] == '#') {
          cout << "Yes" << endl;
          flag = 1;
        }
      }
    }
  }
  if (flag == 0) cout << "No" << endl;
  return 0;
}
