#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int n;
  cin >> n;
  vector<int> v(n);
  for (int i = 0; i < n; i++) cin >> v.at(i);
  sort(v.begin(), v.end());
  float max = (v.at(0) + v.at(1)) / 2;
  for (int i = 2; i < n; i++) {
    max = (max + v.at(i)) / 2;
  }
  cout << max;
  return 0;
}
