#define _USE_MATH_DEFINES
#include <algorithm>
#include <cstdio>
#include <functional>
#include <iostream>
#include <cfloat>
#include <climits>
#include <cstring>
#include <cmath>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <time.h>
#include <unordered_map>
#include <vector>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> i_i;
typedef pair<ll, int> ll_i;
typedef pair<double, int> d_i;
typedef pair<ll, ll> ll_ll;
typedef pair<double, double> d_d;
struct edge { int v, w; };

ll MOD = 1000000009;
ll _MOD = 1000000009;
double EPS = 1e-10;

bool check(vector<string>& S) {
	int H = S.size(), W = S[0].length();
	for (int dy = 0; dy < H; dy++)
		for (int dx = 0; dx < W; dx++) {
			if (dx == 0 && dy == 0) continue;
			vector<string> s = S;
			bool ok = true;
			int cnt = 0;
			for (int y = 0; y < H; y++)
				for (int x = 0; x < W; x++) {
					if (s[y][x] == '.') continue;
					if (x + dx >= W || y + dy >= H || s[y + dy][x + dx] == '.') {
						ok = false;
						continue;
					}
					cnt++;
					s[y + dy][x + dx] = '.';
				}
			if (ok && cnt) return true;
		}
	return false;
}

int main() {
	int H, W; cin >> H >> W;
	vector<string> S(H);
	for (int y = 0; y < H; y++)
		cin >> S[y];
	if (check(S)) {
		cout << "YES" << endl;
		return 0;
	}
	for (int y = 0; y < H; y++)
		reverse(S[y].begin(), S[y].end());
	if (check(S)) {
		cout << "YES" << endl;
		return 0;
	}
	cout << "NO" << endl;
}