#include <iostream>
#include <iomanip>
#include <vector>
#include <valarray>
#include <map>
#include <set>
#include <list>
#include <queue>
#include <stack>
#include <bitset>
#include <utility>
#include <numeric>
#include <algorithm>
#include <functional>
#include <complex>
#include <string>
#include <sstream>

#include <cstdio>
#include <cstdlib>
#include <cctype>
#include <cstring>
#include <cassert>

#include <unordered_set>
#include <unordered_map>
#include <random>
#include <thread>
#include <chrono>

using namespace std;

#define int long long
#define let const auto
#define var auto

#define all(c) c.begin(), c.end()
#define repeat(i, n) for (int i = 0; i < static_cast<int>(n); i++)
#define debug(x) #x << "=" << (x)

#ifdef DEBUG
#define dump(x) std::cerr << debug(x) << " (L:" << __LINE__ << ")" << std::endl
#else
#define dump(x) 
#endif

typedef complex<double> point;

template <typename T>
ostream &operator<<(ostream &os, const vector<T> &v) {
    os << "{";
    for(auto it = v.begin(); it != v.end(); ++it){
        if(it != v.begin()){
            os << ",";
        }
        os << *it;
    }
    return os << "}";
}
template<typename T>
void isort(std::vector<T>& v, std::function<bool(T,T)> comp=less<T>()){
    sort(v.begin(), v.end(), comp);
}
template<typename T>
std::vector<T> sort(std::vector<T> v, std::function<bool(T,T)> comp=less<T>()){
    isort(v);
    return v;
}
template<typename T1, typename T2>
std::vector<T2> rmap(const std::vector<T1>& v, std::function<T2(T1)> f){
    std::vector<T2> t; t.reserve(v.size());
    for(const auto& i: v) t.push_back(f(i));
    return t;
}
std::vector<std::string> split(std::string str, char delim){
    std::vector<std::string> res;
    size_t current = 0, found;
    while((found = str.find_first_of(delim, current)) != std::string::npos){
        res.push_back(std::string(str, current, found - current));
        current = found + 1;
    }
    res.push_back(std::string(str, current, str.size() - current));
    return res;
}
string join(const std::vector<string>& v, string delim){
    string ret = "";
    for(auto it = v.begin(); it != v.end(); ++it){
        if(it != v.begin()){
            ret += delim;
        }
        ret += *it;
    }
    return ret;
}

bool try_solve(const vector<vector<bool> >& field,
               int sy, int sx){
    int h = field.size();
    int w = field[0].size();
    set<pair<int,int>> is_red;
    for(int x=w-1;x>=0;x--){
        for(int y=h-1;y>=0;y--){
            if(field[y][x] &&
               is_red.find(make_pair(y,x)) == is_red.end()){
                int nx = x - sx;
                int ny = y - sy;
                if(nx < 0 || ny < 0) return false;
                if(!field[ny][nx]) return false;
                is_red.insert(make_pair(ny,nx));
            }
        }
    }

    dump(sy);
    dump(sx);
    return true;
}

bool solve(const vector<vector<bool> >& field){
    int h = field.size();
    int w = field[0].size();
    for(int sy=0;sy<=h;sy++){
        for(int sx=0;sx<=w;sx++){
            if(sx == 0 && sy == 0) continue;
            if(try_solve(field,sy,sx)) return true;
        }
    }
    return false;
}

signed main() {
    ios::sync_with_stdio(false);
    cin.tie(0);

    int h, w; cin >> h >> w;
    vector<vector<bool>> field = [&]{
        vector<string> f(h);
        for(auto& s : f) cin >> s;
        return rmap<string, vector<bool>>(f, [&](string r){
                vector<bool> row(w, false);
                for(int i=0;i<r.length();i++){
                    row[i] = r[i] == '#';
                }
                return row;
            });
    }();

    cout << (solve(field) ? "YES" : "NO") << endl;
    return 0;
}