#include <bits/stdc++.h>
using namespace std;
bool mat[55][55];
int dx[4] = {1, 0, -1, 0};
int dy[4] = {0, 1, 0, -1};
int main() {
  int h, w;
  cin >> h >> w;
  for (int i = 1; i <= h; ++i) {
    for (int j = 1; j <= w; ++j) {
      char s;
      cin >> s;
      if (s == '#') mat[i][j] = 1;
    }
  }
  bool f = false;
  for (int i = 1; i <= h; ++i) {
    for (int j = 1; j <= w; ++j) {
      if (mat[i][j]) {
        for (int k = 0; k < (4); ++k)
          if (mat[i + dx[k]][j + dy[k]]) f = true;
      }
    }
  }
  cout << (f ? "Yes" : "No") << endl;
  return 0;
}
