#include <bits/stdc++.h>
using namespace std;
int main() {
  int H, W;
  cin >> H >> W;
  char s[H][W];
  int dx[] = {1, 0, 0, -1}, dy[] = {0, -1, 1, 0};
  for (int i = 0; i < H; i++) {
    for (int j = 0; j < W; j++) {
      cin >> s[i][j];
    }
  }
  for (int i = 0; i < H; i++) {
    for (int j = 0; j < W; j++) {
      if (s[i][j] == '#') {
        for (int k = 0; k < 4; k++) {
          int x = i + dx[k], y = j + dy[k];
          if (s[x][y] == '#') {
            cout << "Yes" << endl;
            return 0;
          }
        }
      }
    }
  }
  cout << "No" << endl;
}
