#include <bits/stdc++.h>
using namespace std;
int main() {
  int a, b;
  cin >> a >> b;
  string h;
  cin >> h;
  for (int m = 1; m < a * b - a - 2; m++) {
    if (h[m] == '#') {
      if (h[m + 1] == '#' || h[m - 1] == '#' || h[m + a] == '#' ||
          h[m - a] == '#') {
        for (int i = 1; i < a * b - a - 2; i++) {
          if (h[i] == '#' && h[i - 1] != '#' && h[i + 1] != '#' &&
              h[i + a] != '#' && h[i - a] != '#') {
            cout << "No" << endl;
            return 0;
          } else {
            cout << "Yes" << endl;
            return 0;
          }
        }
      }
    }
  }
  cout << "Yes" << endl;
}
