#include <bits/stdc++.h>

#define rep(i, n, s) for(int (i) = 0; (i) < (n); (i) += (s))

using namespace std;

int main()
{
  int h, w;
  int start = -1;
  int shap = 0;
  int blue_point = -1;
  int point_length = 0;

  cin >> h >> w;

  vector<char> s(h * w, 0);
  vector<char> check_s(h * w, 0);
  vector<int> shap_index;


  for (int i = 0; i < h * w; ++i)
  {
    cin >> s[i];

    if (s[i] == '#')
    {
      shap++;
      shap_index.push_back(i);
    }

    if (s[i] == '#' && start == -1)
    {
      start = i;
      s[i] = '.';
    }
    // else (s[i] == '#' && blue_point == -1)
    //   blue_point = i;
  }

  if (shap % 2 == 1)
  {
    cout << "NO" << endl;
    exit(0);
  }

  int count = 0;
  while(1)
  {
    check_s = s;
    count++;

    for (int i = 0; i < h * w; ++i)
    {
      if (check_s[i] == '#' && blue_point == -1)
      {
        blue_point = i;
        check_s[i] = '.';
      }

      if (check_s[i] == '#')
      {
        // 赤
        point_length = i - start;
        check_s[i] = '.';

        // 青
        if (blue_point + point_length >= h * w)
        {
          cout << "NO" << endl;
          exit(0);
        }

        if (check_s[blue_point + point_length] == '#')
          check_s[blue_point + point_length] = '.';
        else
        {
          if (i == h * w - 1)
            break;
          else
          {
            blue_point = shap_index[1 + count];
            continue;
          }
        }
      }
    }
    cout << "YES" << endl;
    exit(0);
  }
  cout << "NO" << endl;
}