#define _USE_MATH_DEFINES
#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#include <iomanip>
#include <unordered_map>
#include <unordered_set>
#include <map>
#include <set>
using namespace std;


long long M = 1000000007;

int main(int argc, char const *argv[]){
	int h,m;cin>>h>>m;
	vector<string> b(h);
	for(int i=0;i<h;++i)cin>>b[i];
	for(int i=0;i<h;++i)for(int j=0;j<m;++j){
		if(i==0&&j==0)continue;
		vector<string> bb(h);
		for(int k=0;k<h;++k)bb[k]=b[k].substr(0,m);
		for(int k=0;k<h-i;++k)for(int l=0;l<m-j;++l){
			if(bb[k][l]=='#'){
				if(bb[k+i][l+j]=='#'){
					bb[k][l]='.';
					bb[k+i][l+j]='.';
				}
			}
		}
		bool ok=true;
		for(int k=0;k<h;++k)for(int l=0;l<m;++l){
			if(bb[k][l]=='#')ok=false;
		}
		if(ok){
			// cout<<"YES"<<i<<j<<endl;
			cout<<"YES"<<endl;
			return 0;
		}
	}
	cout<<"NO"<<endl;
	return 0;
}