#include <cstdio>
#include <iostream>
#include <sstream>
#include <fstream>
#include <iomanip>
#include <algorithm>
#include <cmath>
#include <string>
#include <vector>
#include <list>
#include <queue>
#include <stack>
#include <set>
#include <map>
#include <bitset>
#include <numeric>
#include <limits>
#include <climits>
#include <cfloat>
#include <functional>
using namespace std;

bool solve(const vector<string>& s)
{
    int h = s.size();
    int w = s[0].size();

    if(s == vector<string>(h, string(w, '.')))
        return false;

    for(int dy=0; dy<h; ++dy){
        for(int dx=0; dx<w; ++dx){
            if(dy == 0 && dx == 0)
                continue;

            bool ok = true;
            vector<string> t = s;
            for(int y=0; y<h; ++y){
                for(int x=0; x<w; ++x){
                    int y2 = y + dy;
                    int x2 = x + dx;
                    char c = '.';
                    if(y2 < h && x2 < w)
                        c = t[y2][x2];

                    if(t[y][x] == '#'){
                        if(c == '.')
                            ok = false;
                        else if(y2 < h && x2 < w)
                            t[y2][x2] = '.';
                    }
                }
            }

            if(ok)
                return true;
        }
    }

    return false;
}

int main()
{
    int h, w;
    cin >> h >> w;
    vector<string> s(h);
    for(int i=0; i<h; ++i)
        cin >> s[i];

    vector<string> t = s;
    reverse(t.begin(), t.end());

    if(solve(s) || solve(t))
        cout << "YES" << endl;
    else
        cout << "NO" << endl;

    return 0;
}