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****.

no yes no no no yes yes no yes yes yes yes yes yes no yes yes yes yes yes yes yes yes yes yes yes no no no yes yes yes yes no no yes yes yes yes yes no yes yes no no no yes yes no yes yes no no no yes yes yes yes no yes yes yes no
#include <bits/stdc++.h>
using namespace std;
void splitstr(const string &s, vector<string> &v) {
  istringstream in(s);
  copy(istream_iterator<string>(in), istream_iterator<string>(),
       back_inserter(v));
}
void err(vector<string>::iterator it) {}
template <typename T, typename... Args>
void err(vector<string>::iterator it, T a, Args... args) {
  cerr << *it << " = " << a << '\n';
  err(++it, args...);
}
const int maxn = 100005;
const long long INF = (1e9) + 7;
const long double EPS = 1e-8;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  int n;
  cin >> n;
  string s;
  cin >> s;
  for (int i = 1; i <= (int)n; i++) {
    for (int p = 0; p < (int)n; p++) {
      int j = p;
      int q = 0;
      while (j < n) {
        if (s[j] == '.') {
          while (j < n && s[j] == '.') j++;
          q = 0;
        }
        q++;
        if (q == 5) {
          cout << "yes";
          return 0;
        }
        j += i;
      }
    }
  }
  cout << "no";
  return 0;
}
