#include <bits/stdc++.h>
using namespace std;
const int MOD = 1000000007;
const int INF = 100100100;
const double EPS = 0.000000001;
int dx[4] = {1, 0, -1, 0};
int dy[4] = {0, 1, 0, -1};
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  int H, W;
  char S[51][51];
  cin >> H >> W;
  for (int i = 0; i < (H); i++) {
    for (int j = 0; j < (W); j++) {
      cin >> S[i][j];
    }
  }
  bool ans = false;
  for (int i = 0; i < (H); i++) {
    for (int j = 0; j < (W); j++) {
      if (S[i][j] == '#') {
        if ((S[i + dx[0]][i + dy[0]] == '#') ||
            (S[i + dx[1]][i + dy[1]] == '#') ||
            (S[i + dx[2]][i + dy[2]] == '#') ||
            (S[i + dx[3]][i + dy[3]] == '#')) {
          ans = true;
        }
      }
    }
  }
  if (ans)
    cout << "Yes" << endl;
  else
    cout << "No" << endl;
  return 0;
}
