#include <bits/stdc++.h>   using namespace std;   int main() {     int n, m;     cin >> n >> m;     vector<string> a(n);     for (int i = 0; i < n; ++i) cin >> a[i];     for (int j = 0; j < m; ++j) {       vector<int> indx;       for (int i = 0; i < n; ++i) {         if (a[i][j] ==  # ) indx.push_back(i);       }       for (int i = 1; i < indx.size(); ++i) {         if (a[indx[i]] != a[indx[0]]) {           cout <<  No ;           return 0;         }       }     }     cout <<  Yes ;     return 0;   }   