using System;
using System.Collections.Generic;
using System.Collections;
using System.Collections.Specialized;
using System.Linq;
using System.Text;
using System.IO;
using System.Reflection;
using static System.Math;
using System.Numerics;
static class Program{
	const int mod=(int)1e9+7;
	static void Main(){
		Sc sc=new Sc();
		var s=sc.Ia;
		int h=s[0],w=s[1];
		var t=new string[h];
		int n=h*w,g=0;
		for(int i = 0;i<h;i++) {
			t[i]=sc.S;
			for(int j = 0;j<w;j++) {
				if(t[i][j]=='#'){g++;}
			}
		}
		for(int i = 1;i<n;i++) {
			var b=new bool[n];
			int p=0;
			for(int j = 0;j<n;j++) {
				if(!b[j]){
					if(t[j/w][j%w]!='#'){continue;}
					if(j+i<n&&t[(i+j)/w][(i+j)%w]=='#'&&j%w>(i+j)%w){
						b[j]=true;
						b[j+i]=true;
						p+=2;
					}
					else{break;}
				}
			}
			if(p==g&&g!=0){
				Console.WriteLine("YES");
				return;
			}
		}
		for(int i = 1;i<n;i++) {
			var b=new bool[n];
			int p=0;
			for(int j = 0;j<n;j++) {
				if(!b[j]){
					if(t[j/w][j%w]!='#'){continue;}
					if(j+i<n&&t[(i+j)/w][(i+j)%w]=='#'&&j%w<=(i+j)%w){
						b[j]=true;
						b[j+i]=true;
						p+=2;
					}
					else{break;}
				}
			}
			if(p==g&&g!=0){
				Console.WriteLine("YES");
				return;
			}
		}
		Console.WriteLine("NO");
	}
}

public class Sc{
	public int I{get{return int.Parse(Console.ReadLine());}}
	public long L{get{return long.Parse(Console.ReadLine());}}
	public double D{get{return double.Parse(Console.ReadLine());}}
	public string S{get{return Console.ReadLine();}}
	public int[] Ia{get{return Array.ConvertAll(Console.ReadLine().Split(),int.Parse);}}
	public long[] La{get{return Array.ConvertAll(Console.ReadLine().Split(),long.Parse);}}
	public double[] Da{get{return Array.ConvertAll(Console.ReadLine().Split(),double.Parse);}}
	public string[] Sa{get{return Console.ReadLine().Split();}}
	public object[] Oa{get{return Console.ReadLine().Split();}}
	public int[] Ia2{get{return Array.ConvertAll(("0 "+Console.ReadLine()+" 0").Split(),int.Parse);}}
	public int[] Ia3(int a){return Array.ConvertAll((a.ToString()+" "+Console.ReadLine()).Split(),int.Parse);}
	public int[] Ia3(bool a,int b,bool c,int d){return Array.ConvertAll(((a?b.ToString()+" ":"")+Console.ReadLine()+(c?" "+d.ToString():"")).Split(),int.Parse);}
	public long[] La2{get{return Array.ConvertAll(("0 "+Console.ReadLine()+" 0").Split(),long.Parse);}}
	public long[] La3(int a){return Array.ConvertAll((a.ToString()+" "+Console.ReadLine()).Split(),long.Parse);}
	public long[] La3(bool a,int b,bool c,int d){return Array.ConvertAll(((a?b.ToString()+" ":"")+Console.ReadLine()+(c?" "+d.ToString():"")).Split(),long.Parse);}
	public double[] Da2{get{return Array.ConvertAll(("0 "+Console.ReadLine()+" 0").Split(),double.Parse);}}
	public double[] Da3(int a){return Array.ConvertAll((a.ToString()+" "+Console.ReadLine()).Split(),double.Parse);}
	public double[] Da3(bool a,int b,bool c,int d){return Array.ConvertAll(((a?b.ToString()+" ":"")+Console.ReadLine()+(c?" "+d.ToString():"")).Split(),double.Parse);}
	public T[] Arr<T>(int n,Func<T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f();}return a;}
	public T[] Arr<T>(int n,Func<int,T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f(i);}return a;}
	public T[] Arr<T>(int n,Func<string[],T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f(Console.ReadLine().Split());}return a;}
	public T[] Arr<T>(int n,Func<int,string[],T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f(i,Console.ReadLine().Split());}return a;}
}