#include <bits/stdc++.h>
using namespace std;
int main() {
  int h, w;
  cin >> h >> w;
  char s[h][w];
  bool exist = true;
  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] == '#') {
        if (i - 1 >= 0 && s[i][j] == s[i - 1][j]) {
          exist = true;
          continue;
        }
        if (i + 1 <= h && s[i][j] == s[i + 1][j]) {
          exist = true;
          continue;
        }
        if (j - 1 >= 0 && s[i][j] == s[i][j - 1]) {
          exist = true;
          continue;
        }
        if (j + 1 <= w && s[i][j] == s[i][j + 1]) {
          exist = true;
          continue;
        }
        exist = false;
      }
    }
  }
  cout << (exist ? "Yes" : "No") << endl;
}
