#include <bits/stdc++.h>
using namespace std;
int main() {
  int h, w;
  std::cin >> h >> w;
  std::vector<string> v(h);
  for (size_t i = 0; i < h; i++) {
    std::cin >> v.at(i);
  }
  int flag = 0;
  for (size_t i = 0; i < h - 1; i++) {
    for (size_t j = 0; j < w - 1; j++) {
      if (v[i][j] == '#' &&
          (v[i][j] == v[i + 1][j] || v[i][j] == v[i][j + 1])) {
        flag = 1;
      }
    }
  }
  if (flag == 1) {
    std::cout << "Yes" << '\n';
  } else {
    std::cout << "No" << '\n';
  }
}
