#include <bits/stdc++.h>
using namespace std;

int main(){

    int H,W;
    cin >> H >> W;

    bool flag=false;
    vector<string> s;
    string a;
    for(int i = 0; i < H; i++){
        cin >> a;
        s.push_back(a);
        if(s[i].find("#") != string::npos){
            flag=true;
        }
    }

    if(!flag) {
        cout << "NO" << endl;;
        return 0;
    }

    for(int dy = -H; dy < H; dy++){
        for(int dx = -W; dx < W; dx++) {
            if (dx == 0 && dy == 0){
                continue;
            }
            
            auto ss = s;
            bool ng = false;
            int nx, ny;
            for(int i = 0; i < H; i++){
                for(int j = 0; j < W; j++){
                    if(ss[i][j]!='#'){
                        continue;
                    }
                    ny = i + dy;
                    nx = j + dx;
                    
                    if(!(0 <= ny && ny < H)||!(0 <= nx && nx < W)) {
                        ng=true;
                        break;
                    }
                    if(ss[ny][nx]=='#'){
                        ss[ny][nx]='.';
                    }else{
                        ng=true;
                        break;
                    }
                }
                if(ng) break;
            }
            if(!ng){
                cout << "YES" << endl;
                return 0;
            }
        }
    }
    cout << "NO" << endl;
    return 0;
}