#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; m++) {
    if (h[m] == '#' && h[m - 1] == '#' || h[m + 1] == '#' || h[m + a] == '#' ||
        h[m - a] == '#') {
      for (int i = 0; i < a * b; i++) {
        if (h[i] == '#' && h[i - 1] != '#' && h[i + 1] != '#' &&
            h[i + a] != '#' && h[i - a] != '#') {
          cout << "Yes" << endl;
          return 0;
        }
      }
      cout << "No" << endl;
    } else {
      cout << "No" << endl;
      break;
    }
  }
}
