using System;
using System.Collections.Generic;
using System.Linq;

namespace yukicoder
{
    public class Program
    {
        public static void Main()
        {
            var line = Console.ReadLine().Split(' ');
            var h = int.Parse(line[0]);
            var w = int.Parse(line[1]);
            var s = new string[h];
            var a = new List<int[]>();
            int i, j;
            for (i = 0; i < h; i++)
            {
                s[i] = Console.ReadLine();
                for (j = 0; j < w; j++)
                {
                    if (s[i][j] == '#')
                    {
                        var k = new int[2];
                        k[0] = i;
                        k[1] = j;
                        a.Add(k);
                    }
                }
            }
            var t = a.Count;
            var aa = Combination.Generate(t, t / 2, false);
            var A = new List<List<int[]>>();
            var B = new List<List<int[]>>();
            foreach(var x in aa)
            {
                var k = new List<int[]>();
                var l = new List<int[]>();
                for (i = 0; i < t; i++)
                {
                    if (x.Any(value => value == i))
                    {
                        k.Add(a[i]);
                    }
                    else
                    {
                        l.Add(a[i]);
                    }
                }
                A.Add(k);
                B.Add(k);
            }
            bool c = t % 2 == 0;
            if (!c)
            {
                Console.WriteLine("NO");
            }
            for (i = 0; i < A[i].Count; i++)
            {
                var k = A[i].Select(x => new int[2] { x[0] - A[i][0][0], x[1] - A[i][0][1] }).ToArray();
                var l = B[i].Select(x => new int[2] { x[0] - B[i][0][0], x[1] - B[i][0][1] }).ToArray();
                var p = true;
                for (j = 0; j < k.Count(); j++)
                {
                    if (!(k[j][0] == l[j][0] && k[j][1] == l[j][1]))
                    {
                        p = false;
                        break;
                    }
                }
                if (p)
                {
                    c = false;
                    Console.WriteLine("YES");
                    break;
                }
            }
            if (c)
            {
                Console.WriteLine("NO");
            }
        }
        static class Combination
        {
            private static List<List<int>> _comb;
            public static List<List<int>> Generate(int n, int r, bool dupulication)
            {
                _comb = new List<List<int>>();
                CalcCombination(new List<int>(), n, r, dupulication);
                return _comb;
            }
            private static void CalcCombination(List<int> list, int n, int r, bool dupulication)
            {
                if (list.Count == r)
                {
                    _comb.Add(new List<int>(list));
                    return;
                }
                var index = 0;
                if (dupulication)
                {
                    index = list.Any() ? list.Last() : 0;
                }
                else
                {
                    index = list.Any() ? list.Last() + 1 : 0;
                }
                for (int i = index; i < n; i++)
                {
                    list.Add(i);
                    CalcCombination(list, n, r, dupulication);
                    list.Remove(i);
                }
            }
        }
    }
}