using System;
using System.Linq;

namespace No179{
    public class Program{
        public static void Main(string[] args){
            var sr = new StreamReader();
            //---------------------------------
            var H = sr.Next<int>();
            var W = sr.Next<int>();
            var S = sr.Next<string>(H);

            if(S.All(s => s.All(c => c == '.'))){
                Console.WriteLine("NO");
                return;
            }

            Func<int, int, bool> isInside = (x, y) => 0 <= x && x < W && 0 <= y && y < H;
            for(var y = -H; y < H; y++){
                for(var x = -W; x < W; x++){
                    var g = new bool[H, W];
                    for(var i = 0; i < H; i++){
                        for(var j = 0; j < W; j++){
                            if(!g[i, j] && S[i][j] == '#'){
                                g[i, j] = true;
                                if(isInside(j + x, i + y) && S[i + y][j + x] == '#' && !g[i + y, j + x]){
                                    g[i + y, j + x] = true;
                                } else{
                                    goto Next;
                                } 
                            }
                        }
                    }
                    Console.WriteLine("YES");
                    return;
                    Next:;
                }
            }
            Console.WriteLine("NO");
            //---------------------------------
        }
    }

    public class StreamReader{
        private readonly char[] _c = {' '};
        private int _index = -1;
        private string[] _input = new string[0];
        private readonly System.IO.StreamReader _sr = new System.IO.StreamReader(Console.OpenStandardInput());

        public T Next<T>(){
            if(_index == _input.Length - 1){
                _index = -1;
                while(true){
                    string rl = _sr.ReadLine();
                    if(rl == null){
                        if(typeof(T).IsClass) return default(T);
                        return (T)typeof(T).GetField("MinValue").GetValue(null);
                    }
                    if(rl != ""){
                        _input = rl.Split(_c, StringSplitOptions.RemoveEmptyEntries);
                        break;
                    }
                }
            }
            return (T)Convert.ChangeType(_input[++_index], typeof(T), System.Globalization.CultureInfo.InvariantCulture);
        }

        public T[] Next<T>(int x){
            var ret = new T[x];
            for(var i = 0; i < x; ++i) ret[i] = Next<T>();
            return ret;
        }

        public T[][] Next<T>(int y, int x){
            var ret = new T[y][];
            for(var i = 0; i < y; ++i) ret[i] = Next<T>(x);
            return ret;
        }
    }
}