#include <bits/stdc++.h>
using namespace std;
#define REP(i, init, n) for(int i = (int)(init); i < (int)(n); i++)

int main() {
    int H, W;
    cin>>H>>W;
    vector<string> S(H);
    REP(i,0,H) cin >> S[i];
    vector<vector<bool>> Black(H,vector<bool>(W, false)), Blank(H,vector<bool>(W, false));
    REP(i,0,H){
        REP(j,0,W){
            if(S[i][j]=='#') Black[i][j] = true;
        }
    }
    if(Black == Blank){
        cout << "NO" << endl;
        return 0; 
    }
    bool ans = false;

    REP(i, -H, H){
        REP(j, -W, W){
            if(i== 0 && j == 0)  continue;
            vector<vector<bool>> Used(H,vector<bool>(W, false));
            REP(k, 0, H-i){
                REP(l, 0, W-j){
                    if(k<0 || l<0 || k>=H || l>=W || k+i < 0 || l+j <0 || k+i >=H || l+j >= W) continue;
                    if(S[k][l] =='#' && S[k+i][l+j] == '#' && !Used[k][l] && !Used[k+i][l+j]){
                        Used[k+i][l+j] = true;
                        Used[k][l] = true;
                    }
                }
            }
            if(Black == Used) ans = true;
        }
    }
    cout << (ans ? "YES" : "NO" ) << endl;
}