#include <bits/stdc++.h>
using namespace std;
/*{{{*/  //template
#define rep(i,n) for(int i=0;i<n;i++)
constexpr int INF = numeric_limits<int>::max()/2;
constexpr long long LINF = numeric_limits<long long>::max()/3;
#define mp make_pair
#define pb push_back
#define eb emplace_back
#define fi first
#define se second
#define all(v) (v).begin(),(v).end()
#define sz(x) (int)(x).size()
#define debug(x) cerr<<#x<<":"<<x<<endl
#define debug2(x,y) cerr<<#x<<","<<#y":"<<x<<","<<y<<endl
//struct fin{ fin(){ cin.tie(0); ios::sync_with_stdio(false); } } fin_;
struct Double{ double d; explicit Double(double x) : d(x){} };
ostream& operator<<(ostream& os,const Double x){ os << fixed << setprecision(20) << x.d; return os; }
template<typename T> ostream& operator<<(ostream& os,const vector<T>& vec){ os << "["; for(const auto& v : vec){ os << v << ","; } os << "]"; return os; }
template<typename T,typename U> ostream& operator<<(ostream& os,const pair<T,U>& p){ os << "(" << p.first << ","<< p.second <<")"; return os; }
template<typename T> ostream& operator<<(ostream& os,const set<T>& st){ os<<"{"; for(T v:st) os<<v<<","; os <<"}"; return os; }
template<typename T,typename U> inline void chmax(T &x,U y){ if(y>x) x = y; }
template<typename T,typename U> inline void chmin(T &x,U y){ if(y<x) x = y; }
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> pii;
typedef vector<int> vi;
typedef vector<vi> vvi;
ll gcd(ll a,ll b){ if(b==0) return a; else return gcd(b,a%b); }
//constexpr double eps = 1e-14; 
constexpr double eps = 1e-10; 
constexpr ll mod = 1e9+7;
const int dx[]={1,0,-1,0} ,dy[] = {0,1,0,-1};
/*}}}*/

int h,w;
vector<string> tab;

int main(){
    cin>>h>>w;
    tab.resize(h);
    rep(i,h) cin>>tab[i];

    int cnt=0;
    rep(i,h) rep(j,w) if(tab[i][j]=='#') cnt++;
    if(cnt==0 or cnt%2==1){
        cout << "NO" << endl;
        return 0;
    }

    for(int dx=-h+1;dx<h;dx++) for(int dy=-w+1;dy<w;dy++){
        if(dx==0 and dy==0) continue;
        auto s = tab;
        bool f=true;
        [&](){
            rep(x,h) rep(y,w){
                if(s[x][y]=='#'){
                    int nx=x+dx;
                    int ny=y+dy;
                    if(nx<0 or ny<0 or nx>=h or ny>=w or s[nx][ny]!='#'){
                        //cerr << dx << " " << dy << " " << x << " " << y << endl;
                        f=false;
                        return;
                    }
                    s[x][y] = 'R';
                    s[nx][ny] = 'B';
                }
            }
        }();
        if(f){
            //cerr << dx << " "<< dy << endl;
            cout << "YES" << endl;
            return 0;
        }
    }
    cout << "NO" << endl;
}