#include <bits/stdc++.h>
#include <math.h>

#include <algorithm>
#include <array>
#include <atcoder/all>
#include <bitset>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <sstream>
#include <vector>

using namespace std;
using namespace atcoder;

using Graph = vector<vector<int>>;

using ll = long long;
typedef pair<ll, ll> P_ll;
typedef pair<int, int> P;

const ll INF_ll = 1e17;
const int INF = 1e8;
template <class T>
bool chmax(T& a, const T& b) {
  if (a < b) {
    a = b;
    return 1;
  }
  return 0;
}
template <class T>
bool chmin(T& a, const T& b) {
  if (b < a) {
    a = b;
    return 1;
  }
  return 0;
}
template <typename T>
using min_priority_queue = priority_queue<T, vector<T>, greater<T>>;

int main() {
  int H, W;
  cin >> H >> W;
  vector<string> S(H);
  for (int i = 0; i < H; i++) {
    cin >> S[i];
  }

  for (int di = -(H - 1); di <= H - 1; di++) {
    for (int dj = -(W - 1); dj <= W - 1; dj++) {
      if (di == 0 && dj == 0) {
        continue;
      }
      vector<vector<int>> X(H, vector<int>(W, -1));
      int cnt = 0;
      bool ok = true;
      for (int i = 0; i < H; i++) {
        for (int j = 0; j < W; j++) {
          if (S[i][j] == '.') {
            continue;
          }
          if (X[i][j] == 1) {
            continue;
          }
          X[i][j] = 0;
          if (i + di >= H || i + di < 0 || j + dj >= W || j + dj < 0) {
            ok = false;
            continue;
          }
          if (S[i + di][j + dj] == '.') {
            ok = false;
            continue;
          }

          X[i + di][j + dj] = 1;
        }
      }
      if (ok) {
        // cout << di << "," << dj << endl;
        cout << "YES" << endl;
        return 0;
      }
    }
  }
  cout << "NO" << endl;

  return 0;
}