#include <bits/stdc++.h>
using namespace std;
int main(int argc, const char* argv[]) {
  int m, n;
  cin >> n >> m;
  string matrix[50];
  int used[50];
  for (int i = 0; i < 50; i++) {
    used[i] = -1;
  }
  for (int i = 0; i < n; i++) {
    cin >> matrix[i];
  }
  for (int i = 0; i < n; i++) {
    for (int j = 0; j < m; j++) {
      if (matrix[i][j] == '#' && used[j] == -1) {
        used[j] = i;
      }
      if (matrix[i][j] == '#' && used[j] != -1) {
        if (matrix[i] != matrix[used[j]]) {
          cout << "NO";
          return 0;
        }
      }
    }
  }
  cout << "YES";
  return 0;
}
