#include <bits/stdc++.h>
using namespace std;
char A[51][51];
int main() {
  int h, w;
  cin >> h >> w;
  for (int i = 0; i < h; i++) {
    for (int j = 0; j < w; j++) {
      cin >> A[i][j];
    }
  }
  bool ok = false;
  for (int i = 0; i < h; i++) {
    for (int j = 0; j < w; j++) {
      if (A[i][j] == '#') {
        if (A[i][j - 1] == '#' && A[i][j + 1] == '#' && A[i - 1][j] == '#' &&
            A[i + 1][j] == '#')
          ok = true;
      }
    }
  }
  if (ok)
    cout << "Yes\n";
  else
    cout << "No\n";
  return 0;
}
