#define _USE_MATH_DEFINES

#include <iostream>
#include <iomanip>

#include <algorithm>
#include <cmath>

#include <string>
#include <list>
#include <queue>
#include <vector>
#include <complex>

/////////
#define REP(i, x, n) for(int i = x; i < n; i++)
#define rep(i,n) REP(i,0,n)
#define P(p) std::cout<<(p)<<std::endl;
/////////
typedef long long LL;
typedef long double LD;
/////////
using namespace::std;
/////////

int main(void){
    std::cin.tie(0);
    std::ios::sync_with_stdio(false);
    std::cout << std::fixed;//
    //cout << setprecision(6);//
	
	int b[50][50];
	int c[50][50];
	int H,W;
	cin>>H>>W;
	
	rep(i,50)rep(k,50)b[i][k]=-1;

	string str;
	int max = 0;
	rep(i,H){
		cin>>str;
		rep(k,W){
			if(str[k] == '#'){
				b[i][k] = 1;
				++max;
			}
			else{
				b[i][k] = 0;
			}
		}
	}
	//
	if(max%2==1 || max==0){//少なくとも１塗る：２マス以上黒、０のＹＥＳは無い
		P("NO");
		return 0;
	}
	//
	int count = 0;
	for(int dx = -W+1; dx<W;++dx){
	for(int dy = 0; dy<H;++dy){
		count = 0;
		rep(h,H)rep(w,W){
			c[h][w] = b[h][w];
		}
		for(int pos=0;pos<H*W ;++pos){
			if(c[pos/W][pos%W]==1){
				c[pos/W][pos%W] = 0;//赤
				if( dy + pos/W < H && 
					dx + pos%W < W &&
					dx + pos%W >= 0 &&
					c[dy + pos/W][dx + pos%W] == 1){
					c[dy + pos/W][dx + pos%W] = 0;//青
					++count;
				}
				else{
					break;
				}
			}
		}
		if(count == max/2){
			P("YES");
			return 0;
		}
	}
	}
	P("NO");
	return 0;
}