#include <bits/stdc++.h>
using namespace std;
const int N = 55;
int n, m;
string s[N];
int main() {
  cin >> n >> m;
  for (int i = 0; i < n; i++) cin >> s[i];
  for (int j = 0; j < m; j++) {
    vector<string> pos;
    for (int i = 0; i < n; i++)
      if (s[i][j] == '#') pos.emplace_back(s[i]);
    for (size_t i = 1; i < pos.size(); i++)
      if (pos[i] != pos[i - 1]) {
        printf("No");
        return 0;
      }
  }
  printf("Yes");
  return 0;
}
