#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef pair<ll,ll> pl;
typedef vector<pl> vp;
#define fore(i,a,b) for(ll i=(ll)(a);i<=(ll)(b);++i)
#define rep(i,n) fore(i,0,(n)-1)
#define rfore(i,a,b) for(ll i=(ll)(b);i>=(ll)(a);--i)
#define rrep(i,n) rfore(i,0,(n)-1)
#define all(x) (x).begin(),(x).end()
const ll INF=1001001001;
const ll LINF=1001001001001001001;
const ll D4[]={0,1,0,-1,0};
const ll D8[]={0,1,1,0,-1,-1,1,-1,0};
template<class T>
bool chmax(T &a,const T &b){if(a<b){a=b;return 1;}return 0;}
template<class T>
bool chmin(T &a,const T &b){if(b<a){a=b;return 1;}return 0;}

bool e[55][55];
void solve(){
    ll h,w;cin>>h>>w;
    vector<string> s(h);rep(i,h)cin>>s[i];

    ll cnt=0;
    rep(i,h)rep(j,w)if(s[i][j]=='#')cnt++;
    if(!cnt){
        cout<<"NO"<<endl;
        return;
    }
    
    rep(i,h)fore(j,-(w-1),w-1){
        if(i==0&&j==0)continue;
        memset(e,0,sizeof(e));
        rep(k,h)rep(l,w)if(s[k][l]=='#')e[k][l]=1;
        bool ok=1;
        rep(k,h)rep(l,w){
            if(!e[k][l])continue;
            if(k+i>=h||l+j>=w||!e[k+i][l+j])ok=0;
            else e[k+i][l+j]=0;
        }
        if(ok){
            cout<<"YES"<<endl;
            return;
        }
    }
    cout<<"NO"<<endl;
}

int main(){
    cin.tie(0);
    ios::sync_with_stdio(0);
    solve();
}