#include <iostream>
#include <vector>
#include <algorithm>
#include <iomanip>
using namespace std;

typedef long long LL;

bool check(vector<string> board, int dx, int dy){
    int cnt = 0;
    for(int y = 0; y < board.size(); y++){
        for(int x = 0; x < board[0].size(); x++){
            if(board[y][x] == '#'){
                cnt++;
                board[y][x] = '.';
                if(y+dy >= board.size() || x+dx >= board[0].size() || x+dx < 0) return false;
                if(board[y+dy][x+dx] != '#') return false;
                board[y+dy][x+dx] = '.';
            }
        }
    }
    if(cnt == 0) return false;
    return true;
}

int main(){
    int H, W;
    cin >> H >> W;
    vector<string> board(H);
    for(int i = 0; i < H; i++){
        cin >> board[i];
    }
    bool flag = false;
    for(int dy = 0; dy < H; dy++){
        for(int dx = -W; dx < W; dx++){
            if(check(board, dx, dy)) flag = true;
        }
    }
    if(flag){
        cout << "YES" << endl;
    }else{
        cout << "NO" << endl;
    }
    return 0;
}