#include <bits/stdc++.h>
#include<iostream>
#include<iomanip>
#include<string>
#include<algorithm>
#include<vector>
#include<set>
#include<list>
#include<queue>
#include<math.h>
#include<bitset>
using ll = long long;
using namespace std;


int main(){
    int h, w;
    cin >> h >> w;
    string s;
    vector<string> v(h);
    for (int i = 0; i < h; i++) cin >> v[i];
    for (int i = 0; i < h; i++){
        for (int j = -w + 1; j < w; j++){
            int dy = i, dx = j;
            bool no = false, yes = false;
            vector<string> tmp = v;
            if (dy == 0 && dx == 0) continue;
            for (int k = 0; k < h; k++){
                for (int l = 0; l < w; l++){
                    if (tmp[k][l] == '#'){
                        tmp[k][l] = 'R';
                        if (k + dy >= 0 && k + dy < h && l + dx >= 0 && l + dx < w){
                            if(v[k+dy][l+dx] == '#'){
                                tmp[k+dy][l+dx] = 'B';
                                yes = true;
                            } else {
                                no = true;
                                yes = false;
                                break;
                            }
                        } else {
                            no = true;
                            yes = false;
                            break;
                        }
                    }
                }
                if (no) break;
            }
            if (yes){
                cout << "YES" << endl;
                return 0;
            }
        }
    }
    cout << "NO" << endl;
}