#pragma GCC optimize("O3")
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
#pragma GCC target("avx,avx2")
#include <bits/stdc++.h>
#define INF 1000000001LL
#define LNF 1000000000000000001LL
#define MOD 1000000007LL
#define MAX 502
#define long long long
#define all(x) x.begin(),x.end()
using namespace std;

int n,m;
bool check(vector<string> &pan, int x, int y)
{
    bool vis[n][m];
    memset(vis,0,sizeof vis);

    int cnt = 0;
    for(int i = 0; i<n; i++)
    {
        for(int j = 0; j<m; j++)
        {
            if(pan[i][j] == '#')
                cnt++;
            if(vis[i][j] || pan[i][j] == '.')
                continue;

            vis[i][j] = true;

            if(i+x >=n || j+y >= m)
                return false;
            if(vis[i+x][j+y] || pan[i+x][j+y] == '.')
                return false;
            vis[i+x][j+y] = true;
        }
    }
    if(cnt < 2)
        return false;
    return true;
}
int main()
{
	ios_base::sync_with_stdio(0); 
    cin.tie(0);

    
    cin >> n >> m;

    vector<string> pan(n);

    for(int i = 0; i<n; i++)
        cin >> pan[i];

    for(int i = 0; i<n; i++)
    {
        for(int j = 0; j<m; j++)
        {
            if(check(pan,i,j))
            {
                cout << "YES\n";
                return 0;
            }
        }
    }
    cout << "NO\n";
    return 0;
}