#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  scanf("%d", &n);
  char s[200];
  memset(s, '.', sizeof(s));
  scanf("%s", &s);
  for (int i = 0; i < n - 4; i++) {
    if (s[i] == '*') {
      for (int j = 1; n > i + j * 4; j++) {
        if (s[i + j] == '*' && s[i + (j << 1)] == '*' &&
            s[i + (j * 3)] == '*' && s[i + (j << 2)] == '*') {
          printf("yes");
          return 0;
        }
      }
    }
  }
  printf("no");
  return 0;
}
