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