#include <bits/stdc++.h>
using namespace std;
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());
  vector<double> sum(n);
  sum[0] = (v[0] + v[1]) / 2.0;
  for (int j = 0; j < n - 2; j++) {
    sum[j + 1] = (sum[j] + v[j + 2]) / 2.0;
  }
  cout << (sum[n - 2] + v[n - 1]) / 2.0 << endl;
}
