#include <bits/stdc++.h>
using namespace std;
int main() {
  int h, w;
  cin >> h;
  cin >> w;
  string s[h];
  for (int n = 0; n < h; n++) {
    cin >> s[n];
  }
  bool found = false;
  for (int x = 1; x < w - 1; x++) {
    for (int y = 1; y < h - 1; y++) {
      if (s[y][x] != '#') continue;
      if (s[y - 1][x] != '#') continue;
      if (s[y + 1][x] != '#') continue;
      if (s[y][x - 1] != '#') continue;
      if (s[y][x + 1] != '#') continue;
      found = true;
      break;
    }
  }
  if (found)
    cout << "Yes" << endl;
  else
    cout << "No" << endl;
}
