#include <cstdlib>
#include <cmath>
#include <climits>
#include <cfloat>
#include <map>
#include <set>
#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <sstream>
#include <complex>
#include <stack>
#include <queue>
#include <cstdio>
#include <cstring>
#include <iterator>
#include <bitset>
#include <unordered_set>
#include <unordered_map>
//#include <utility>
//#include <memory>
//#include <functional>
//#include <deque>
//#include <cctype>
//#include <ctime>
//#include <numeric>
//#include <list>
//#include <iomanip>

//#if __cplusplus >= 201103L
//#include <array>
//#include <tuple>
//#include <initializer_list>
//#include <forward_list>
//
//#define cauto const auto&
//#else

//#endif

using namespace std;


typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;

typedef vector<int> vint;
typedef vector<vector<int> > vvint;
typedef vector<long long> vll, vLL;
typedef vector<vector<long long> > vvll, vvLL;

#define VV(T) vector<vector< T > >

template <class T>
void initvv(vector<vector<T> > &v, int a, int b, const T &t = T()){
    v.assign(a, vector<T>(b, t));
}

template <class F, class T>
void convert(const F &f, T &t){
    stringstream ss;
    ss << f;
    ss >> t;
}


#define reep(i,a,b) for(int i=(a);i<(b);++i)
#define rep(i,n) reep((i),0,(n))
#define ALL(v) (v).begin(),(v).end()
#define PB push_back
#define F first
#define S second
#define mkp make_pair
#define RALL(v) (v).rbegin(),(v).rend()
// #define DEBUG
#ifdef DEBUG
#define dump(x)  cout << #x << " = " << (x) << endl;
#define debug(x) cout << #x << " = " << (x) << " (L" << __LINE__ << ")" << " " << __FILE__ << endl;
#else
#define dump(x) 
#define debug(x) 
#endif

#define MOD 1000000007LL
#define EPS 1e-8
static const int INF=1<<24;
int h,w;
vector<string> s;
bool check(int a,int b,int c,int d){
	if(0<=a&&a<c&&0<=b&&b<d) return true;
	return false;
}
bool foo2(int y1,int x1,int y2,int x2){
	bool f1=check(y1,x1,h,w);
	bool f2=check(y2,x2,h,w);
	if(f1&&!f2){
		if(s[y1][x1]=='#'){
			return false;
		}
		return true;
	}
	if(!f1&&f2){
		if(s[y2][x2]=='#'){
			return false;
		}
		return true;
	}
	if(!f1&&!f2) return true;
	if(s[y1][x1]=='#'&&y1==y2&&x1==x2) return false;
	if(s[y1][x1]=='.'&&s[y2][x2]=='.') return true;
	if(s[y1][x1]!='#'&&s[y2][x2]=='#') return false;
	if(s[y1][x1]=='#'&&s[y2][x2]!='#') return false;
	s[y1][x1]='-';
	s[y2][x2]='-';
	return true;
}
// bool foo(int y,int x){
	// rep(i,h){
		// rep(j,w){
			// if(!foo2(i,j,y+i,x+j)){
				// if(y==0&&x==3){
					// cout<<i<<" "<<j<<endl;
				// }
				// return false;
			// }
		// }
	// }
	// return true;
// }
bool foo(int yy,int xx,int y,int x,int cnt){
	int t=0;
	rep(i,h){
		rep(j,w){
			// if(!check(i,j,h,w)) continue;
			if(s[i][j]=='#'){
				if(!check(i-yy+y,j-xx+x,h,w)){
					return false;
				}
				if(s[i-yy+y][j-xx+x]=='#'){
					s[i][j]='-';
					s[i-yy+y][j-xx+x]='-';
					t++;
				}
				else return false;
			}
		}
	}
	if(t==cnt) return true;
	return false;
}
void mainmain(){
	// int h,w;
	cin>>h>>w;
	vector<string> v(h);
	rep(i,h) cin>>v[i];
	int a=-1,b=-1;
	rep(i,h){
		rep(j,w){
			if(v[i][j]=='#'){
				a=i;
				b=j;
				break;
			}
		}
		if(a!=-1) break;
	}
	int su=0;
	rep(i,h){
		rep(j,w){
			if(v[i][j]=='#'){
				su++;
			}
		}
	}
	if(su%2){
		puts("NO");
		return;
	}
	su/=2;
	if(a==-1&&b==-1){
		puts("NO");
		return;
	}
	if(su==0){
		puts("NO");
		return;
	}
	reep(i,-h,h+1){
		reep(j,-w,w+1){
			if(i==a&&j==b){
				continue;
			}
			// cout<<i<<" "<<j<<endl;
			s=v;
			if(foo(a,b,i,j,su)){
				puts("YES");
				return;
			}
		}
	}
	puts("NO");
}


main() {
    mainmain();
}