#include <bits/stdc++.h>
using namespace std;
int main(void) {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  int N = 0;
  cin >> N;
  vector<int> v(N);
  for (int i = 0; i < N; i++) cin >> v[i];
  sort(v.begin(), v.end());
  double price = 0;
  for (int i = 1; i < v.size(); i++) {
    int sum = 0;
    if (price == 0)
      sum = v[i - 1] + v[i];
    else
      sum = price + v[i];
    price = sum / 2.0;
  }
  cout << price << "\n";
  return 0;
}
