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import java.util.ArrayList;
import java.util.Scanner;

public class MysticalMosaic {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner scanner=new Scanner(System.in);
		int n=scanner.nextInt();
		int m=scanner.nextInt();
		scanner.nextLine();
		boolean can=true;
		ArrayList<Row>rows=new ArrayList<>();
		for(int i=0;i<n;i++){
			Row row=new Row();
			
			String c=scanner.nextLine();
			for(int w=0;w<m;w++)if(c.charAt(w)=='#')row.positionOfBlack.add(w);
			
			rows.add(row);
		}
		for(int i=0;i<n;i++){
			for(int j=i+1;j<n;j++){
				if(!rows.get(i).positionOfBlack.equals(rows.get(j).positionOfBlack) && exists(rows.get(i).positionOfBlack,rows.get(j).positionOfBlack)){
					can=false;
					break;
				}
			}
			if(!can)break;
		}
		if(can)System.out.println("yes");
		else System.out.println("no");
	}
	static boolean exists(ArrayList<Integer>a,ArrayList<Integer>b){
		boolean x[]=new boolean [50];
		for(int i=0;i<a.size();i++)x[a.get(i)]=true;
		for(int i=0;i<b.size();i++)if(x[b.get(i)]==true)return true;
		return false;
	}
	
}

class Row{
	public ArrayList<Integer> positionOfBlack=new ArrayList<>(); 
}
