#include <bits/stdc++.h>
using namespace std;
int powInt(int x, int y) {
  int ans = 1;
  for (int i = 0; i < y; ++i) {
    ans *= x;
  }
  return ans;
}
int main() {
  int n;
  double a;
  cin >> n;
  vector<double> vec(n);
  for (int i = 0; i < n; ++i) {
    cin >> a;
    vec.at(i) = a;
  }
  sort(vec.begin(), vec.end());
  reverse(vec.begin(), vec.end());
  double amount = 0;
  for (int j = 0; j < n - 1; ++j) {
    double p = j;
    amount += vec.at(j) / pow(2.0, p + 1.0);
  }
  amount += vec.at(vec.size() - 1) / powInt(2, vec.size() - 1);
  cout << amount << endl;
}
