#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;

int main() {
 	int n;
  	cin >> n;
  	vector<int> ele(n, 0);
  	for (int i = 0; i < n; i++) cin >> ele[i];
  	double ans = 0;
  	sort(ele.begin(), ele.end());
  	ans = (ele[0] + ele[1]) / 2.0;
  	for (int i = 2; i < n; i++) ans = (ans + ele[i]) / 2.0
    cout << ans << endl;
}