#include <bits/stdc++.h>
using namespace std;
int main() {
  int H, W;
  cin >> H >> W;
  vector<vector<char>> s(H, vector<char>(W));
  for (int i = 0; i < H; i++) {
    for (int j = 0; j < W; j++) {
      cin >> s.at(i).at(j);
    }
  }
  int dx[] = {0, 0, 1, -1};
  int dy[] = {1, -1, 0, 0};
  bool b = false;
  for (int i = 0; i < H; i++) {
    for (int j = 0; j < W; j++) {
      char c_tmp = s.at(i).at(j);
      if (c_tmp == '.') {
        b = true;
        continue;
      }
      if (c_tmp == '#') {
        for (int k = 0; k < 4; k++) {
          if (i + dx[k] < 0 || i + dx[k] >= H || j + dy[k] < 0 ||
              j + dy[k] >= W) {
            continue;
          }
          char c_tmp2 = s.at(i + dx[k]).at(j + dy[k]);
          if (c_tmp2 == '#') {
            b = true;
            break;
          }
        }
      }
    }
  }
  if (b) {
    cout << "Yes" << endl;
  } else {
    cout << "No" << endl;
  }
}
