#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;

bool check(vector<string> bb, int i, int j){
	int h=bb.size(),m=bb[0].length();
	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;
	}
	return ok;
}

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];
	bool existsh=false;
	for(int i=0;i<h;++i)for(int j=0;j<m;++j)if(b[i][j]=='#')existsh=true;
	if(!existsh){
		cout<<"NO"<<endl;
		return 0;
	}
	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[h-k-1].substr(0,m);
		if(check(b,i,j)||check(bb,i,j)){
			// cout<<"YES"<<i<<j<<endl;
			cout<<"YES"<<endl;
			return 0;
		}
	}
	cout<<"NO"<<endl;
	return 0;
}