#include <bits/stdc++.h>
using namespace std;
char str[105];
int judge(int n) {
  int i, j, len;
  for (i = 0; i < n; i++) {
    if (str[i] == '*')
      for (j = i + 1; j < n; j++)
        if (str[j] == '*') {
          len = j - i;
          if (j + 3 * len < n && str[j + len] == '*' &&
              str[j + 2 * len] == '*' && str[j + 3 * len] == '*')
            return 1;
        }
  }
  return 0;
}
int main() {
  int n;
  while (scanf("%d", &n) != EOF) {
    scanf("%s", str);
    if (judge(n))
      printf("yes\n");
    else
      printf("no\n");
  }
  return 0;
}
