// Standard I/O
#include <iostream>
#include <sstream>
#include <cstdio>
// Standard Library
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <cmath>
// Template Class
#include <complex>
#include <string>
#include <vector>
#include <list>
#include <set>
#include <map>
#include <queue>
#include <stack>
// Container Control
#include <algorithm>

using namespace std;

#define rep( i, n ) for( int i = 0; i < n; ++i )
#define irep( i, n ) for( int i = n-1; i >= 0; --i )
#define reep( i, s, n ) for ( int i = s; i < n; ++i )
#define ireep( i, n, s ) for ( int i = n-1; i >= s; --i )
#define foreach(itr, x) for( typeof(x.begin()) itr = x.begin(); itr != x.end(); ++itr)

#define mp( a, b ) make_pair( a, b )
#define pb( a ) push_back( a )
#define all( v ) v.begin(), v.end()
#define fs first
#define sc second
#define vc vector

// for visualizer.html
double SCALE = 1.0;
double OFFSET_X = 0.0;
double OFFSET_Y = 0.0;
#define LINE(x,y,a,b) cerr << "line(" << SCALE*(x) + OFFSET_X << ","	\
	<< SCALE*(y) + OFFSET_Y << ","										\
	<< SCALE*(a) + OFFSET_X << ","										\
	<< SCALE*(b) + OFFSET_Y << ")" << endl;
#define CIRCLE(x,y,r) cerr << "circle(" << SCALE*(x) + OFFSET_X << ","	\
	<< SCALE*(y) + OFFSET_Y << ","										\
	<< SCALE*(r) << ")" << endl;

typedef long long ll;
typedef complex<double> Point;

typedef pair<int, int> pii;
typedef pair<int, pii> ipii;
typedef vector<int> vi;
typedef vector<double> vd;
typedef vector< vector<int> > vii;
typedef vector< vector<double> > vdd;

typedef vector<int>::iterator vi_itr;

const int IINF = 1 << 28;
const double INF = 1e30;
const double EPS = 1e-10;
const double PI = acos(-1.0);

// Direction : L U R D
const int dx[] = { -1, 0, 1, 0};
const int dy[] = { 0, -1, 0, 1 };

int H, W;
string str[50];
bool check1 ( int x, int y )
{
	int used[50][50] = { 0 };
	rep(i, H) rep(j, W){
		if( str[i][j] == '.' || used[i][j] == 2 ) continue;
		if( i+y < 0 || j+x < 0 || i+y >= H || j+x >= W ) return false;
		if( str[i+y][j+x] == '.' ) return false;
		
		used[i][j] = 1;
		used[i+y][j+x] = 2;
	}
	
	return true;
}

bool check2 ( int x, int y )
{
	int used[50][50] = { 0 };
	for( int i = H-1; i >= 0; --i ) rep(j, W){
		if( str[i][j] == '.' || used[i][j] == 2 ) continue;
		if( i+y < 0 || j+x < 0 || i+y >= H || j+x >= W ) return false;
		if( str[i+y][j+x] == '.' ) return false;
		
		used[i][j] = 1;
		used[i+y][j+x] = 2;
	}
	
	return true;
}

int main()
{
	cin >> H >> W;
	rep(i, H) cin >> str[i];

	bool ans = true;
	rep(i, H) rep(j, W) if(str[i][j] == '#') ans = false;

	if( ans ){ cout << "NO" << endl; return 0; }
	
	rep(i, H) rep(j, W){
		if( i == 0 && j == 0 ) continue;
		ans |= check1(j, i);
		ans |= check2(j, -i);
	}
	
	cout << (ans ? "YES" : "NO") << endl;
}