#include <bits/stdc++.h>
using namespace std;
int main() {
  int h, w;
  cin >> h >> w;
  char s[h][w];
  for (int i = 0; i < h; i++) {
    for (int j = 0; j < w; j++) {
      cin >> s[i][j];
    }
  }
  int dx[4] = {1, -1, 0, 0};
  int dy[4] = {0, 0, 1, -1};
  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 i2 = i + dx[k];
          int j2 = j + dy[k];
          if (0 <= i2 && i2 <= h - 1 && 0 <= j2 && j2 <= w - 1 &&
              s[i2][j2] == '#') {
            cout << "Yes" << endl;
            return 0;
          }
        }
      }
    }
  }
  cout << "No" << endl;
  return 0;
}
