#include <bits/stdc++.h>
using namespace std;
int dx[4] = {0, 0, 1, -1};
int dy[4] = {1, -1, 0, 0};
int main() {
  int h, w;
  cin >> h >> w;
  string s[h];
  bool flag = true;
  for (int i = 0; i < h; i++) {
    cin >> s[i];
  }
  int cnt = 0;
  for (int i = 0; i < h; i++) {
    for (int j = 0; j < w; j++) {
      if (s[i][j] == '#') {
        cnt++;
        for (int k = 0; k < 4; k++) {
          int x = j + dx[k];
          int y = i + dy[k];
          if (x < 0 || y < 0 || x > w || y > h) continue;
          if (s[y][x] == '#') flag = false;
        }
      }
      if (!flag) {
        cout << "Yes" << endl;
        return 0;
      }
    }
  }
  if (cnt == 0) {
    cout << "Yes" << endl;
    return 0;
  }
  cout << "No" << endl;
}
