#include<bits/stdc++.h>
using namespace std;
#define ALL(x) begin(x),end(x)
#define rep(i,n) for(int i=0;i<(n);i++)
#define debug(v) cout<<#v<<":";for(auto x:v){cout<<x<<' ';}cout<<endl;
#define mod 1000000007
using ll=long long;
const int INF=1000000000;
const ll LINF=1001002003004005006ll;
int dx[]={1,0,-1,0},dy[]={0,1,0,-1};
// ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}
template<class T>bool chmax(T &a,const T &b){if(a<b){a=b;return true;}return false;}
template<class T>bool chmin(T &a,const T &b){if(b<a){a=b;return true;}return false;}

struct IOSetup{
    IOSetup(){
        cin.tie(0);
        ios::sync_with_stdio(0);
        cout<<fixed<<setprecision(12);
    }
} iosetup;
 
template<typename T>
ostream &operator<<(ostream &os,const vector<T>&v){
    for(int i=0;i<(int)v.size();i++) os<<v[i]<<(i+1==(int)v.size()?"":" ");
    return os;
}
template<typename T>
istream &operator>>(istream &is,vector<T>&v){
    for(T &x:v)is>>x;
    return is;
}


signed main(){
    int h,w;cin>>h>>w;
    vector<string> s(h);
    cin>>s;

    for(int si=0;si<h;si++)for(int sj=0;sj<w;sj++)if(si or sj){
        vector<vector<int>> c(h,vector<int>(w,0));
        bool f=true;
        rep(i,h)rep(j,w)if(f){
            if(s[i][j]=='.'){
                c[i][j]=3;
                continue;
            }

            if(c[i][j]) continue;
            if(i+si>=h or j+sj>=w){
                f=false;
                break;
            }
            if(s[i+si][j+sj]=='.'){
                f=false;
                break;
            }
            c[i][j]=0;
            c[i+si][j+sj]=1;
        }
        if(f){
            cout<<"YES"<<endl;
            return 0;
        }
    }    
    cout<<"NO"<<endl;
    return 0;
}