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/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
import java.util.*;
/**
 *
 * @author SNEHITH
 */
public class Main {
    public static void main(String args[]){
        Scanner sc = new Scanner(System.in);
        int m = sc.nextInt();
        int n = sc.nextInt();
        int k=0,count=0,failure=0,prev=0,curr=0;
//        sc.next();
        String s[] = new String[m+1];
        for(int i=0;i<m+1; i++){
                s[i] = sc.nextLine();
        }
        for(int i=0; i < n; i++){
            for(int j=1; j<m+1;j++){
//                System.out.print(s[j].charAt(k));
                if(s[j].charAt(k) == '#'){
                    count++;
                    prev = curr;
                    curr = j;
                }
                if(count >= 2){
//                        System.out.println("s[prev]"+s[prev] + "curr"+ s[curr]);

                    if(s[prev].equals(s[curr]) == false){
                        failure = 1;
//                        System.out.println("s[prev]"+s[prev] + "curr"+ s[curr]);
                    }
                }
            }
 //           System.out.println(count);
            count=0;
            k++;
  //          System.out.println();
        }
        if(failure == 1)
            System.out.println("NO");
        else
            System.out.println("YES");
        
    }
}
