#include<bits/stdc++.h>
typedef long long ll;
using namespace std;
int INF = 1LL << 30;
int MOD = 1e9+7;
main(){
    int H,W;
    cin >> H >> W;
    vector<string> S(H);
    for(int i = 0;i < H;i++)cin >> S[i];
    bool flag = 1;
    for(int i = 0;i < H;i++)for(int j = 0;j < W;j++)if(S[i][j] == '#')flag = 0;
    if(flag){
        cout << "NO" << endl;
        return 0;
    }
    for(int i = 0;i < H;i++){
        for(int j = -W+1;j < W;j++){
            vector<string> str(S);
            bool ok = 1;
            for(int k = 0;k < H;k++){
                for(int l = 0;l < W;l++){
                    if(str[k][l] == '#'){
                        if(k + i < 0 || k + i >= H || l + j < 0 || l + j >= W || str[k+i][l+j] != '#'){
                            ok = 0;
                            k = H;break;
                        }
                        str[k][l] = 'x';
                        str[k + i][l + j] = 'o';
                    }
                }
            }
            for(int k = 0;k < H;k++){
                //cout << str[k] << endl;
                for(int l = 0;l < W;l++){
                    if(str[k][l] == '#')ok = 0;
                }
            }
            if(ok && (i | j)){
                //cout << i << " " << j << endl;
                cout << "YES" << endl;
                return 0;
            }
        }
    }
    cout << "NO" << endl;
}