#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, i, len, k;
  bool fl = false;
  char s[101];
  cin >> n;
  cin >> s;
  for (len = 1; len < n && !fl; len++) {
    for (int j = 0; j < n && !fl; j++) {
      for (i = j; s[i] != '*' && i < n; i++)
        ;
      if (i + len * 4 < n)
        if (s[i] == '*' && s[i + len] == '*' && s[i + len * 2] == '*' &&
            s[i + len * 3] == '*' && s[i + len * 4] == '*')
          fl = true;
    }
  }
  if (fl == true)
    cout << "yes";
  else
    cout << "no";
  return 0;
}
