#include <bits/stdc++.h>
using namespace std;
vector<long long> a;
int main() {
  long long n, m;
  cin >> n >> m;
  vector<string> a;
  for (long long i = 0; i < n; i++) {
    string te;
    cin >> te;
    long long p = a.size();
    bool f = 1;
    for (long long j = 0; j < p; j++) {
      if (te == a[j]) {
        f = 0;
      }
    }
    if (f) {
      a.push_back(te);
    }
  }
  long long p = a.size();
  for (long long i = 0; i < p - 1; i++) {
    for (long long j = i + 1; j < p; j++) {
      for (long long k = 0; k < m; k++) {
        if (a[i][k] == a[j][k] && a[i][k] == '#') {
          cout << "No";
          return 0;
        }
      }
    }
  }
  cout << "Yes";
  return 0;
}
