#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;
}

struct mint {
    int x;
    mint() : x(0) {}
    mint(int64_t y) : x(y >= 0 ? y % mod : (mod - (-y) % mod) % mod) {}
    mint& operator+=(const mint& p){
        if((x += p.x) >= mod)   x -= mod;
        return *this;
    }
    mint& operator-=(const mint& p){
        if((x -= p.x) < 0)  x += mod;
        return *this;
    }
    mint& operator*=(const mint& p){
        x = (int)(1LL * x * p.x % mod);
        return *this;
    }
    mint& operator/=(const mint& p){
        *this *= p.inverse();
        return *this;
    }
    mint operator-() const { return mint(-x); }
    mint operator+(const mint& p) const { return mint(*this) += p; }
    mint operator-(const mint& p) const { return mint(*this) -= p; }
    mint operator*(const mint& p) const { return mint(*this) *= p; }
    mint operator/(const mint& p) const { return mint(*this) /= p; }
    bool operator==(const mint& p) const { return x == p.x; }
    bool operator!=(const mint& p) const { return x != p.x; }
    mint pow(int64_t n) const {
        mint res = 1, mul = x;
        while(n > 0){
            if(n & 1)   res *= mul;
            mul *= mul;
            n >>= 1;
        }
        return res;
    }
    mint inverse() const { return pow(mod - 2); }
    friend ostream& operator<<(ostream& os, const mint& p){
        return os << p.x;
    }
    friend istream& operator>>(istream& is, mint& p){
        int64_t val;
        is >> val;
        p = mint(val);
        return is;
    }
};

mint dp[5001][5001];

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 + 1; dx < h; ++dx){
        for(int dy = -w + 1; 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 || 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;
}