#include <bits/stdc++.h>
int main() {
  int n, i, j, ans = 0;
  char c[101];
  scanf("%d", &n);
  scanf("%s", c);
  int l;
  for (l = 1; l <= n; l++) {
    for (i = 0; i < n - 4 * l; i++) {
      if (c[i] == '*' && c[i + l] == '*' && c[i + 2 * l] == '*' &&
          c[i + 3 * l] == '*' && c[i + 4 * l] == '*') {
        ans = 1;
        break;
      }
    }
    if (ans == 1) break;
  }
  if (ans == 1)
    printf("yes\n");
  else
    printf("no\n");
  return 0;
}
