#include <bits/stdc++.h>
using namespace std;
using ll = long long;
template <typename T>
using V = std::vector<T>;
using Vi = V<int>;
using VVi = V<V<int>>;
using Vll = V<ll>;
using VVll = V<V<ll>>;
using Vs = V<string>;
template <typename T1, typename T2>
using P = std::pair<T1, T2>;
using Pii = P<int, int>;
using Pdd = P<double, double>;
template <typename T1, typename T2>
using M = std::map<T1, T2>;
using Msi = M<string, int>;
const ll MOD = 1e9 + 7;
int main() {
  int n;
  cin >> n;
  Vi v(n);
  for (int i = 0; i < (int)(n); ++i) {
    cin >> v[i];
  }
  sort((v).begin(), (v).end(), greater<int>());
  double cnt = 0;
  for (int i = 0; i < (int)(n); ++i) {
    if (i != n - 1) {
      cnt += v[i] * pow(0.5, i + 1);
    } else {
      cnt += v[i] * pow(0.5, i);
    }
  }
  printf("%.5fl\n", cnt);
  return 0;
}
