#include <bits/stdc++.h>
using namespace std;
int main() {
  int H, W;
  cin >> H >> W;
  cout << endl;
  cout << endl;
  cout << endl;
  string ans = "Yes";
  char *ptr1 = new char[W];
  char *ptr2 = new char[W];
  for (int j = 0; j < W; j++) {
    cin >> ptr1[j];
  }
  for (int i = 1; i <= H; i++) {
    while (i % 2 == 0) {
      for (int j = 0; j < W; j++) {
        cin >> ptr1[j];
        if (ptr2[j] == '#') {
          if ((j + 1 < W && ptr2[j + 1] == '#') || ptr1[j] == '#') {
          } else {
            ans = "No";
            i = H;
            break;
          }
        }
      }
      i = H;
      break;
    }
    while (i % 2 == 1) {
      for (int j = 0; j < W; j++) {
        cin >> ptr2[j];
        if (ptr1[j] == '#') {
          if ((j + 1 < W && ptr1[j + 1] == '#') || ptr2[j] == '#') {
          } else {
            ans = "No";
            i = H;
            break;
          }
        }
      }
      i = H;
      break;
    }
  }
  cout << ans << endl;
  return 0;
}
