#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<int> v(n);
  for (int i = 0; i < (int)(n); ++i) {
    cin >> v.at(i);
  }
  sort((v).begin(), (v).end());
  double ans = (v.at(0) + v.at(1)) / 2;
  for (int i = ((int)(1)); i < (int)(n - 1); ++i) {
    ans = (ans + v.at(i + 1)) / 2;
  }
  cout << ans << endl;
  return 0;
}
