#include<bits/stdc++.h>
using namespace std;

#define all(v) v.begin(),v.end()
using ll = long long;
using ull = unsigned long long;
using vll=vector<ll>;
using vvll = vector<vector<ll>>;

int main(){
    ll H,W;
    cin >>H>>W;
    vector<vector<char>> S(H,vector<char>(W));
    for(int i=0;i<H;i++){
        for(int j=0;j<W;j++){
            cin >>S[i][j];
        }
    }
    for(int i=-H;i<H;i++){
        for(int j=-W;j<W;j++){
            if(i==0&&j==0)continue;
            vvll A(H,vll(W,-1));
            bool a=true;
            for(int i2=0;i2<H;i2++){
                for(int j2=0;j2<W;j2++){
                    if(S[i2][j2]=='.'||A[i2][j2]!=-1)continue;
                    A[i2][j2]=1;
                    ll i3=i2+i,j3=j2+j;
                    if(!(0<=i3&&i3<H&&0<=j3&&j3<W)){
                        a=false;
                        break;
                    }
                    if(S[i3][j3]=='.')a=false;
                    A[i3][j3]=0;
                }
            }
            if(a){
                cout << "YES" << endl;
                return 0;
            }
        }
    }
    cout << "NO" << endl;
}