#include <bits/stdc++.h>
using namespace std;
const double eps = 1e-9;
const int MOD = 1e9 + 7;
const int INF = 0x3f3f3f3f;
const int MAXN = 5e2 + 10;
inline int read() {
  int ret = 0, sgn = 1;
  char ch = getchar();
  while (ch < '0' || ch > '9') {
    if (ch == '-') sgn = -1;
    ch = getchar();
  }
  while (ch >= '0' && ch <= '9') {
    ret = ret * 10 + ch - '0';
    ch = getchar();
  }
  return ret * sgn;
}
char a[MAXN][MAXN];
int b[MAXN][MAXN];
int main() {
  int n, m;
  scanf("%d%d", &n, &m);
  for (int i = 1; i < n + 1; i++) {
    scanf("%s", a[i]);
  }
  for (int i = 1; i < n + 1; i++)
    for (int j = 1; j < m + 1; j++) {
      if (a[i][j - 1] == '*')
        b[i][j] = 1;
      else
        b[i][j] = 0;
    }
  int nn = -1;
  int mm = -1;
  int cnt;
  int lx;
  bool tb = true;
  for (int i = 2; i < n; i++) {
    cnt = 0;
    lx = 0;
    for (int j = 1; j < m + 1; j++) {
      if (b[i][j] == 1) {
        if (lx == 0) lx = 1;
        if (lx == 3) {
          lx = 2;
          break;
        }
        cnt++;
      } else {
        if (lx == 1) lx = 3;
      }
    }
    if (lx == 2) {
      tb = false;
      break;
    }
    if (cnt >= 3) {
      nn = i;
      break;
    }
  }
  for (int i = 2; i < m; i++) {
    cnt = 0;
    lx = 0;
    for (int j = 1; j < n + 1; j++) {
      if (b[j][i] == 1) {
        if (lx == 0) lx = 1;
        if (lx == 3) {
          lx = 2;
          break;
        }
        cnt++;
      } else {
        if (lx == 1) lx = 3;
      }
    }
    if (lx == 2) {
      tb = false;
      break;
    }
    if (cnt >= 3) {
      mm = i;
      break;
    }
  }
  if (nn == -1 || mm == -1 || tb == false) {
    printf("NO\n");
  } else {
    if (b[nn][mm] == 0 || b[nn + 1][mm] == 0 || b[nn - 1][mm] == 0 ||
        b[nn][mm + 1] == 0 || b[nn][mm - 1] == 0) {
      printf("NO\n");
    } else {
      bool pd = true;
      for (int i = 1; i < n + 1; i++) {
        if (i == nn) continue;
        for (int j = 1; j < m + 1; j++) {
          if (j == mm) continue;
          if (b[i][j] == 1) {
            pd = false;
            break;
          }
        }
        if (!pd) break;
      }
      if (pd)
        printf("YES\n");
      else
        printf("NO\n");
    }
  }
  return 0;
}
