#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int main() {
  int cnt = 0;
  vector<int> tate{0, -1, 0, 1};
  vector<int> yoko{-1, 0, 1, 0};
  int h, w;
  cin >> h >> w;
  vector<string> field;
  for (int i = 0; i < (int)(h); i++) {
    string s;
    cin >> s;
    field.push_back(s);
  }
  for (int i = 0; i < (int)(h); i++) {
    for (int j = 0; j < (int)(w); j++) {
      if (field[i][j] == '#') {
        for (int k = 0; k < (int)(4); k++) {
          if (i + tate[k] >= 0 && i + tate[k] < h && j + yoko[k] >= 0 &&
              j + yoko[k] < w) {
            if (field[i + tate[k]][j + yoko[k]] == '#') cnt++;
          }
        }
      }
    }
  }
  if (cnt > 0)
    cout << "Yes" << endl;
  else
    cout << "No" << endl;
}
