#include <bits/stdc++.h>
const int64_t cc = pow(10, 9);
bool sort_pair(std::pair<std::string, int64_t> origin,
               std::pair<std::string, int64_t> another) {
  return origin.second > another.second;
}
int main() {
  std::string word = "aa";
  int64_t a, b, c, d, e;
  std::cin >> a;
  std::cin >> b;
  std::vector<std::string> list;
  for (int i = 0; i < b; i++) {
    std::cin >> word;
    list.push_back(word);
  }
  bool oo = false;
  for (int i = 0; i < b; i++) {
    for (int r = 1; r < a; r++) {
      if (list[i][r] == '#' && list[i][r] == list[i][r - 1]) {
        oo = true;
      }
    }
  }
  for (int i = 0; i < a; i++) {
    for (int r = 1; r < b; r++) {
      if (list[r][i] == '#' && list[r][i] == list[r - 1][i]) {
        oo = true;
      }
    }
  }
  if (oo) {
    std::cout << "Yes\n";
  } else {
    std::cout << "No\n";
  }
}
