#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, m, i, j, ii, jj;
  cin >> n >> m;
  char a[111][111];
  for (i = 0; i < n; i++) cin >> a[i];
  for (i = 0; i < n; i++) {
    for (j = 0; j < m; j++) {
      for (ii = 0; ii < n; ii++) {
        for (jj = 0; jj < m; jj++) {
          if (a[i][j] == '#' && a[ii][jj] == '#') {
            int cnt = 0;
            if (a[i][jj] == '#') cnt++;
            if (a[ii][j] == '#') cnt++;
            if (cnt == 1) {
              cout << "NO";
              return 0;
            }
          }
        }
      }
    }
  }
  cout << "YES";
}
