#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<int> a(n);
  for (int i = 0; n > i; i++) {
    cin >> a[i];
  }
  sort(a.begin(), a.end());
  double nw = (double)(a[0] + a[1]) / 2;
  for (int i = 2; n > i; i++) {
    nw = (double)(nw + a[2]) / 2;
  }
  cout << fixed << setprecision(10) << nw << endl;
}
