using System;
using System.IO;
using System.Linq;
using System.Text;
using System.Collections.Generic;
using System.Diagnostics;
using System.Numerics;
using Enu = System.Linq.Enumerable;

class Program
{
    int H, W;
    string[] grid;

    public void Solve()
    {
        H = Reader.Int();
        W = Reader.Int();
        grid = Reader.StringArray(H);
        int count = string.Join("", grid).Count(c => c == '#');
        if (count == 0 || count % 2 == 1)
        {
            Console.WriteLine("NO");
            return;
        }

        for (int dr = -H + 1; dr < H; dr++)
            for (int dc = -W + 1; dc < W; dc++)
                if (OK(dr, dc))
                {
                    Console.WriteLine("YES");
                    return;
                }

        Console.WriteLine("NO");
    }

    private bool OK(int dr, int dc)
    {
        if (dr == 0 && dc == 0) return false;
        Func<int, int, bool> IsInside = (r, c) => r >= 0 && r < H && c >= 0 && c < W;

        bool[,] seen = new bool[H, W];
        for (int r = 0; r < H; r++)
            for (int c = 0; c < W; c++)
                if (!seen[r, c] && grid[r][c] == '#')
                {
                    seen[r, c] = true;
                    int nr = r + dr, nc = c + dc;
                    if (!IsInside(nr, nc) || seen[nr, nc] || grid[nr][nc] != '#') return false;
                    seen[nr, nc] = true;
                }
        for (int r = 0; r < H; r++)
            for (int c = 0; c < W; c++)
                if (grid[r][c] == '#' && !seen[r, c]) return false;

        return true;
    }
}


class Entry { static void Main() { new Program().Solve(); } }
class Reader
{
    private static TextReader reader = Console.In;
    private static readonly char[] separator = { ' ' };
    private static readonly StringSplitOptions op = StringSplitOptions.RemoveEmptyEntries;
    private static string[] A = new string[0];
    private static int i;
    private static void Init() { A = new string[0]; }
    public static void Set(TextReader r) { reader = r; Init(); }
    public static void Set(string file) { reader = new StreamReader(file); Init(); }
    public static bool HasNext() { return CheckNext(); }
    public static string String() { return Next(); }
    public static int Int() { return int.Parse(Next()); }
    public static long Long() { return long.Parse(Next()); }
    public static double Double() { return double.Parse(Next()); }
    public static int[] IntLine() { return Array.ConvertAll(Split(Line()), int.Parse); }
    public static int[] IntArray(int N) { return Enu.Range(0, N).Select(i => Int()).ToArray(); }
    public static int[][] IntTable(int H) { return Enu.Range(0, H).Select(i => IntLine()).ToArray(); }
    public static string[] StringArray(int N) { return Enu.Range(0, N).Select(i => Line()).ToArray(); }
    public static string Line() { return reader.ReadLine().Trim(); }
    private static string[] Split(string s) { return s.Split(separator, op); }
    private static string Next() { CheckNext(); return A[i++]; }
    private static bool CheckNext()
    {
        if (i < A.Length) return true;
        string line = reader.ReadLine();
        if (line == null) return false;
        if (line == "") return CheckNext();
        A = Split(line);
        i = 0;
        return true;
    }
}