#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using P = pair<int, int>;
using G = vector<vector<int>>;
int main() {
  int n;
  cin >> n;
  vector<int> v(n);
  for (int i = 0; i < n; i++) cin >> v[i];
  sort(v.begin(), v.end());
  double ans = 0.0;
  for (int i = 0; i < n - 1; i++) {
    ans += (double)v[n - i - 1] / (double)(1 << (i + 1));
  }
  ans += (double)v[0] / (double)(1 << (n - 1));
  cout << fixed << setprecision(6) << ans << endl;
  return 0;
}
