#include <bits/stdc++.h>

int main() {
	
	int H,W;
	std::cin >> H >> W;
	std::vector<std::string> S(H);
	for(auto&v:S)std::cin >> v;
	bool ans = false;
	bool exist = false;
	for(int y=-H+1;!ans&&y<H;++y){
		for(int x=-W+1;!ans&&x<W;++x){
			if(!x&&!y)continue;
			bool result = true;
			auto S2 = S;
			for(int h=0;result&&h<H;++h){
				for(int w=-W+1;result&&w<W;++w){
					if(S2[h][w]!='#')continue;
					exist = true;
					S2[h][w]='R';
					int h2=h+y,w2=w+x;
					if(h2<0||H<=h2||w2<0||W<=w2){
						result = false;
						break;
					}
					if(S2[h2][w2]=='#'){
						S2[h2][w2]='B';
						continue;
					}
					result = false;
				}
			}
			if(result)ans = true;
		}
	}
	ans = ans && exist;
	std::cout << (ans?"YES":"NO") << std::endl;
}