#include <bits/stdc++.h>
using namespace std;
signed main() {
  int H, W;
  cin >> H >> W;
  int dh[] = {-1, 0, 1, 0};
  int dw[] = {0, -1, 0, 1};
  string board[H];
  for (int i = 0; i < H; i++) cin >> board[i];
  bool flag = false;
  for (int i = 0; i < H; i++) {
    for (int j = 0; j < W; j++) {
      if (board[i][j] == '#') {
        for (int k = 0; k < 4; k++) {
          int h = i + dh[k];
          int w = j + dw[k];
          if (0 <= h && h < H && 0 <= w && w < W && board[i][j] == '#')
            flag = true;
        }
      }
    }
  }
  cout << (flag ? "Yes" : "No") << endl;
  return 0;
}
