#include<bits/stdc++.h>
using namespace std;
#define rep(i,n) for(ll i=0;i<n;i++)
#define repl(i,l,r) for(ll i=(l);i<(r);i++)
#define per(i,n) for(ll i=(n)-1;i>=0;i--)
#define perl(i,r,l) for(ll i=r-1;i>=l;i--)
#define fi first
#define se second
#define pb push_back
#define ins insert
#define pqueue(x) priority_queue<x,vector<x>,greater<x>>
#define all(x) (x).begin(),(x).end()
#define CST(x) cout<<fixed<<setprecision(x)
#define rev(x) reverse(x);
using ll=long long;
using vl=vector<ll>;
using vvl=vector<vector<ll>>;
using pl=pair<ll,ll>;
using vpl=vector<pl>;
using vvpl=vector<vpl>;
const ll MOD=1000000007;
const ll MOD9=998244353;
const int inf=1e9+10;
const ll INF=4e18;
const ll dy[8]={-1,0,1,0,1,1,-1,-1};
const ll dx[8]={0,-1,0,1,1,-1,1,-1};
template<class T> inline bool chmin(T& a, T b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template<class T> inline bool chmax(T& a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}

int main(){
    ll h,w;cin >> h >>w;
    vector<string> g(h);rep(i,h)cin >> g[i];
    ll ans=0;rep(i,h)rep(j,w)if(g[i][j]=='#')ans++;
    rep(i,h){
        rep(j,w){
            ll cnt=0;
            rep(k,h){
                rep(l,w){
                    if(i+k<h&&l+j<w){
                        if(g[k][l]=='#'&&g[i+k][j+l]=='#')cnt++;
                    }
                }
            }
            //cout << cnt <<endl;
            if(ans==cnt*2)cout << "YES" <<endl,exit(0);
        }
    }
    cout << "NO" <<endl;
}