#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <queue>
#include <string>
#include <map>
#include <set>
#include <stack>
#include <tuple>
#include <deque>
#include <array>
#include <numeric>
#include <bitset>
#include <iomanip>
#include <cassert>
#include <chrono>
#include <random>
#include <limits>
#include <iterator>
#include <functional>
#include <sstream>
#include <fstream>
#include <complex>
#include <cstring>
#include <unordered_map>
#include <unordered_set>
using namespace std;

using ll = long long;
using P = pair<int, int>;
constexpr int INF = 1001001001;
constexpr int mod = 1000000007;
// constexpr int mod = 998244353;

template<class T>
inline bool chmax(T& x, T y){
    if(x < y){
        x = y;
        return true;
    }
    return false;
}
template<class T>
inline bool chmin(T& x, T y){
    if(x > y){
        x = y;
        return true;
    }
    return false;
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

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

    for(int dx = -h; dx <= h; ++dx){
        for(int dy = -w; dy <= w; ++dy){
            if(dx == 0 && dy == 0)  continue;
            vector<vector<bool>> used(h, vector<bool>(w));
            for(int x = 0; x < h; ++x){
                for(int y = 0; y < w; ++y){
                    if(used[x][y] || s[x][y] == '.')    continue;
                    int nx = x + dx, ny = y + dy;
                    if(nx < 0 || nx >= h || ny < 0 || ny >= w || used[nx][ny] || s[nx][ny] == '.')  continue;
                    used[x][y] = used[nx][ny] = true;
                }
            }
            bool ok = true;
            for(int x = 0; x < h; ++x){
                for(int y = 0; y < w; ++y){
                    if(s[x][y] == '#' && !used[x][y])   ok = false;
                }
            }
            if(ok){
                cout << "YES\n";
                return 0;
            }
        }
    }
    
    cout << "NO\n";

    return 0;
}