#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<int> a;
  while (n--) {
    int x;
    cin >> x;
    a.push_back(x);
  }
  sort(a.begin(), a.end());
  int best = 0;
  do {
    int now = a[0];
    for (auto i : a) {
      now = (i + now) / 2;
    }
    best = max(best, now);
  } while (next_permutation(a.begin(), a.end()));
  cout << fixed << setprecision(6) << best << "\n";
}
