#include <stdio.h>
#include <stdlib.h>
#include <string>
#include <utility>
#include <vector>
#include <algorithm>
#include <functional>
#include <iostream>

using namespace std;

int size;
vector<int> v;
bool *check;

bool search (int cnt , int sub) {
    if (cnt == size / 2) return true;
    for (int i = 0; i < size; i++) {
        if (check[i]) continue;
        check[i] = true;
        for (int j = 0; j < size; j++) {
            if (check[j]) continue;
            if (abs(v[i] - v[j]) == sub) {
                check[j] = true;
                if (search(cnt + 1 , sub)) return true;
                check[j] = false;
            }
        }
        check[i] = false;
        return false;
    }
}

bool solve () {
    size = v.size();
    if (size % 2 == 1) return false;
    check = new bool[size];
    for (int i = 1; i < size; i++) check[i] = false;
    check[0] = true;
    for (int i = 1; i < size; i++) {
        check[i] = true;
        if (search(1,v[i] - v[0])) return true;
        check[i] = false;
    }
    return false;
}

int main () {
    cin.tie(0);
    ios::sync_with_stdio(false);
    
    int h , w;
    cin >> h >> w;
    
    string s;
    for (int i = 0; i < h; i++) {
        cin >> s;
        for (int j = 0; j < w; j++) {
            if (s.at(j) == '#') {
                v.push_back(i << 8 | j);
            }
        }
    }
    
    cout << (solve() ? "YES" : "NO") << "\n";
}