#include<iostream>
#include<vector>
#include<string>
#include<string.h>

using namespace std;

int main(){
    int H,W;

    cin >> H;
    cin >> W;

    bool flag;
    bool nothing=true;
    string row;
    vector< vector<string> > map;       //original
    vector< vector<string> > map_prac;  //copy
    map.resize(H);
    map_prac.resize(H);
    for(int i=0;i<H;i++){
        map[i].resize(W);
        map_prac[i].resize(W);
    }

    for(int i=0;i<H;i++){
        cin >> row;
        for(int j=0;j<W;j++){
            map[i][j]=row[j];
        }
    }

    for(int i=-H+1;i<H;i++){
        for(int j=-W+1;j<W;j++){//moving valiation 2499 ways
            if(i==0&&j==0)continue; //skip (0,0) move
            //cout << "moving [" << i << "]&[" << j << "]" << endl;
            map_prac = map;
            flag=true;
            for(int k=0;k<H;k++){
                for(int l=0;l<W;l++){
                    if(map_prac[k][l].compare(".")==0){ // "." found!
                    }else{ // "#" found!
                        nothing=false;
                        if((0<=(k+i)) && ((k+i)<H) && (0<=(l+j)) && ((l+j)<W)){ // check sticking out
                            if(map_prac[k+i][l+j].compare("#")==0){
                                map_prac[k+i][l+j]=".";
                            }else{
                                //cout << "false[" << i << "]&[" << j << "]" << endl;
                                flag=false;
                                break;
                            }
                        }else{
                            flag=false;
                            break;
                        }
                    }
                }
                if(!flag)break;// if flag is false ,finalize one moving validation
            }
            if(flag)break;
        }
        if(flag)break;
    }

    if(nothing) {
        cout << "NO" << endl;
    }else if(flag) {
        cout << "YES" << endl;
    }else{
        cout << "NO" << endl;
    }
    return 0;
}