#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, tmp;
  double ans;
  vector<int> all;
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> tmp;
    all.push_back(tmp);
  }
  sort(all.begin(), all.end());
  ans = all.at(0);
  for (int i = 1; i < all.size(); i++) {
    ans = (ans + all.at(i)) / 2.0;
  }
  cout << ans << endl;
  return 0;
}
