#include <bits/stdc++.h>
using namespace std;
char s[600][600];
int x, y;
int main() {
  cin >> x >> y;
  for (int i = 0; i < x; i++) {
    cin >> s[i];
  }
  bool che = false;
  for (int i = 0; i < x - 2; i++) {
    if (che) break;
    for (int j = 1; j < y - 1; j++) {
      if (s[i][j] == '*' && s[i + 1][j] == '*' && s[i + 2][j] == '*') {
        s[i][j] = '.';
        s[i + 1][j] = '.';
        s[i + 2][j] = '.';
        int h = i + 1;
        for (int k = i + 3; k < x; k++) {
          if (s[k][j] == '*') {
            s[k][j] = '.';
            h = k - 1;
          } else
            break;
        };
        che = false;
        for (int k = i + 1; k <= h; k++) {
          if (s[k][j - 1] == '*' && s[k][j + 1] == '*') {
            che = true;
            for (int l = j - 1; l >= 0; l--) {
              if (s[k][l] == '*')
                s[k][l] = '.';
              else
                break;
            }
            for (int l = j + 1; l < y; l++) {
              if (s[k][l] == '*')
                s[k][l] = '.';
              else
                break;
            }
            break;
          }
        }
        if (!che) {
          cout << "NO" << endl;
          return 0;
        }
        break;
      }
    }
  }
  for (int i = 0; i < x; i++) {
    for (int j = 0; j < y; j++) {
      if (s[i][j] == '*') {
        cout << "NO" << endl;
        return 0;
      }
    }
  }
  if (che)
    cout << "YES" << endl;
  else
    cout << "NO" << endl;
  return 0;
}
