#include <iostream>
#include <vector>
#include <cstdio>
#include <sstream>
#include <map>
#include <string>
#include <algorithm>
#include <queue>
#include <cmath>
#include <set>
using namespace std;

int main(){
	int h, w;
	cin >> h >> w;
	vector<string> s(h);
	for(int i=0; i<h; i++){
		cin >> s[i];
	}

	bool ok = false;
	for(int dy=0; dy<h; dy++){
		for(int dx=0; dx<w; dx++){
			if(dx == dy && dx == 0) continue;
			bool valid = true;
			vector<vector<int>> c(h, vector<int>(w,-1));
			int cnt = 0;

			for(int i=0; i<h && valid; i++){
				for(int j=0; j<w && valid; j++){
					int red = 0;
					int blue = 0;

					if(s[i][j] == '.') continue;
					if(c[i][j] != -1) continue;
					int x = j, y = i;
					int color = 0;
					while(!( y < 0 || y >= h || x < 0 || x >= w )){
						if(s[y][x] == '.'){
							break;
						}
						(color?red:blue) += 1;
						c[y][x] = color;
						color ^= 1;
						y += dy;
						x += dx;
					}

					x = j-dx, y = i-dy;
					color = 1;
					while(!( y < 0 || y >= h || x < 0 || x >= w )){
						if(s[y][x] == '.'){
							break;
						}
						(color?red:blue) += 1;
						c[y][x] = color;
						color ^= 1;
						y -= dy;
						x -= dx;
					}

					if(!(red>0 && blue>0 && red==blue)){
						valid = false;
						break;
					}else{
						cnt++;
					}

				}
			}
			if(valid){
				cout << "YES" << endl;
				return 0;
			}
		}
	}
	cout << "NO" << endl;
	return 0;
}