#include <bits/stdc++.h>   char s[100][100];   int main() {     int n, m, ans = 0;     scanf( %d%d , &n, &m);     for (int i = 1; i <= n; i++) scanf( %s , s[i] + 1);     for (int i = 1; i < n; i++) {       for (int j = i + 1; j <= n; j++) {         int f = 0, g = 0;         for (int k = 1; k <= m; k++)           if (s[i][k] !=  .  || s[j][k] !=  . ) {             if (s[i][k] == s[j][k])               f = 1;             else               g = 1;           }         if (f == g && f) {           printf( No );           return 0;         }       }     }     printf( Yes );   }   