#define _CRT_SECURE_NO_WARNINGS
//#define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
//#define int ll
//#define endl "\n"
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int,int> pii;
#define all(c) (c).begin(), (c).end()
#define loop(i,a,b) for(ll i=a; i<ll(b); i++)
#define rep(i,b) loop(i,0,b)
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define mt make_tuple
template<class T> ostream & operator<<(ostream & os, vector<T> const &);
template<int n, class...T> typename enable_if<(n>=sizeof...(T))>::type _ot(ostream &, tuple<T...> const &){}
template<int n, class...T> typename enable_if<(n< sizeof...(T))>::type _ot(ostream & os, tuple<T...> const & t){ os << (n==0?"":" ") << get<n>(t); _ot<n+1>(os, t); }
template<class...T> ostream & operator<<(ostream & os, tuple<T...> const & t){ _ot<0>(os, t); return os; }
template<class T, class U> ostream & operator<<(ostream & os, pair<T,U> const & p){ return os << "(" << p.first << ", " << p.second << ") "; }
template<class T> ostream & operator<<(ostream & os, vector<T> const & v){ rep(i,v.size()) os << v[i] << (i+1==(int)v.size()?"":" "); return os; }
template<class T> inline bool chmax(T & x, T const & y){ return x<y ? x=y,true : false; }
template<class T> inline bool chmin(T & x, T const & y){ return x>y ? x=y,true : false; }
#ifdef DEBUG
#define dump(...) (cerr<<#__VA_ARGS__<<" = "<<mt(__VA_ARGS__)<<" ["<<__LINE__<<"]"<<endl)
#else
#define dump(...)
#endif
// ll const mod = 1000000007;
// ll const inf = 1LL<<60;

char g[60][60];
int h,w;
int c;

bool check(int dx, int dy){
    int cnt = 0;
    bool used[60][60] = {};
    rep(y,h)rep(x,w){
        if(y+dy >= h || x+dx >= w  || x+dx < 0 || y+dy < 0) continue;
        if(used[y][x] || used[y+dy][x+dx]) continue;
        if(g[y][x] == '#' && g[y+dy][x+dx] == '#'){
            used[y+dy][x+dx] = used[y][x] = true;
            cnt += 2;
        }
    }
    return cnt == c && cnt;
}

signed main(){
    ios_base::sync_with_stdio(0); cin.tie(0);
    while(cin >> h >> w){
        c = 0;
        rep(i,h){
            cin >> g[i];
            rep(j,w) if(g[i][j]=='#') c++;
        }
        bool ok = false;
        for(int dy=-h-10; dy<=h+10 && !ok; dy++){
            for(int dx=-w-10; dx<=w+10 && !ok; dx++){
                if(dx==0 && dy==0) continue;
                if(check(dx,dy)){
                    ok = true;
                }
            }
        }
        puts(ok ? "YES" : "NO");
    }
}