#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<int> v(n);
  for (int i = 0; i < (int)(n); i++) cin >> v[i];
  sort(v.begin(), v.end());
  long double ans = (long double)v[0] + v[1];
  int cnt = 2;
  for (int i = 2; i < n; i++) {
    ans += cnt * v[i];
    cnt *= 2;
  }
  ans = (long double)ans / cnt;
  cout << setprecision(12) << ans << endl;
  return 0;
}
