#include <bits/stdc++.h>
using namespace std;
char s[105];
int main(void) {
  int n, f;
  while (cin >> n) {
    scanf("%s", s);
    f = 0;
    for (int l = (1); l <= (n); ++l) {
      for (int j = (0); j <= (n - 4 * l - 1); ++j) {
        if (j + 4 * l >= n) break;
        if (s[j] == '*' && s[j + l] == '*' && s[j + 2 * l] == '*' &&
            s[j + 3 * l] == '*' && s[j + 4 * l] == '*') {
          f = 1;
          break;
        }
      }
      if (f) break;
    }
    if (f)
      cout << "yes\n";
    else
      cout << "no\n";
  }
  return 0;
}
