#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  priority_queue<long double, vector<long double>, greater<long double>> ans;
  for (int i = 0; i < n; i++) {
    int temp;
    cin >> temp;
    ans.push(temp);
  }
  for (int i = 0; i < n - 1; i++) {
    int x, y;
    x = ans.top();
    ans.pop();
    y = ans.top();
    ans.pop();
    long double temp = (long double)((long double)(x + y) / (long double)2.0);
    ans.push(temp);
  }
  cout << setprecision(60) << ans.top() << "\n";
  return 0;
}
