#include <bits/stdc++.h>
using namespace std;
int dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};
int main() {
  int h, w;
  int grid[55][55];
  cin >> h >> w;
  for (int i = 0; i < h; i++) {
    for (int j = 0; j < w; j++) {
      char ch;
      cin >> ch;
      if (ch == '#')
        grid[i][j] = 2;
      else
        grid[i][j] = 0;
    }
  }
  for (int i = 0; i < h; i++) {
    for (int j = 0; j < w; j++) {
      if (grid[i][j] == 0) continue;
      for (int k = 0; k < 4; k++) {
        int x = j + dx[k], y = i + dy[k];
        if (x < 0 || x >= w || y < 0 || y >= h) continue;
        if (grid[y][x]) {
          cout << "Yes" << endl;
          return 0;
        }
      }
    }
  }
  cout << "No" << endl;
  return 0;
}
