import std.stdio, std.conv, std.string;
import std.array, std.range, std.algorithm, std.container;
import std.math, std.random, std.bigint, std.datetime, std.format;
string read(){ static string[] ss; while(!ss.length) ss = readln.chomp.split; string res = ss[0]; ss.popFront; return res; }

int DEBUG_LEVEL = 0;
void print()(){ writeln(""); }
void print(T, A ...)(T t, lazy A a){ write(t), print(a); }
void print(int level, T, A ...)(T t, lazy A a){ if(level <= DEBUG_LEVEL) print(t, a); }

void main(string[] args){
	if(args.length > 1 && args[1] == "-debug"){
		if(args.length > 2 && args[2].isNumeric) DEBUG_LEVEL = args[2].to!int;
		else DEBUG_LEVEL = 1;
	}
	
	long h = read.to!long;
	long w = read.to!long;
	
	bool[][] xs;
	foreach(i; 0 .. h){
		xs ~= readln.chomp.map!(x => x == '#').array;
	}
	
	string ans = "NO";
	bool[][] ys = new bool[][](h, w);
	foreach(a; 0 .. h) foreach(b; -w + 1 .. w){
		bool flag = 1;
		foreach(i; 0 .. h) foreach(j; 0 .. w) ys[i][j] = xs[i][j];
		foreach(i; 0 .. h) foreach(j; 0 .. w){
			if(! ys[i][j]) continue;
			ys[i][j] = 0;
			if(i + a < h && j + b >= 0 && j + b < w && ys[i + a][j + b]) ys[i + a][j + b] = 0;
			else flag = 0;
		}
		if(flag) ans = "YES";
	}
	
	ans.writeln;
}