#include "bits/stdc++.h"
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
#define rep(i,n) for(ll i=0;i<(ll)(n);i++)
#define all(a) (a).begin(),(a).end()
#define pb emplace_back
#define INF (1e9+1)

int h,w;
bool solve(vector<string> vs, int dh, int dw){
    rep(i,h){
        rep(j,w){
            if(vs[i][j]=='#'){
                int ddy = i+dh;
                int ddx = j+dw;
                if(ddx<0 || ddy<0 || ddx>=w || ddy>=h || vs[ddy][ddx]!='#')return false;
                vs[i][j] = 'R';
                vs[ddy][ddx] = 'B';
            }
        }
    }
    
    rep(i,h)rep(j,w){
        if(vs[i][j]=='#')return false;
    }
    return true;
}

int main(){
    cin>>h>>w;
    vector<string> vs(h);
    rep(i,h)cin>>vs[i];
    
    
    bool ans = false;
    
    for(int i=0;i<=49;i++){
        for(int j=0;j<=49;j++){
            if(i==0&&j==0)continue;
            ans |= solve(vs,i,j);
        }
    }
    if(ans)cout<<"YES"<<endl;
    else cout<<"NO"<<endl;
}