#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<int> res(n);
  for (int i = 0; i < n; i++) cin >> res[i];
  float ans = 0;
  sort(res.begin(), res.end());
  float prev = ((float)res[0] + res[1]) / 2;
  for (int i = 2; i < res.size(); i++) {
    prev = (prev + res[i]) / 2;
    ans = prev;
  }
  cout << ans;
  return 0;
}
