#include <bits/stdc++.h>
using namespace std;
void solve() {
  int n;
  cin >> n;
  vector<int> gu(n);
  for (int i = 0; i < n; i++) {
    cin >> gu[i];
  }
  sort(gu.begin(), gu.end());
  double maxv = 0;
  do {
    double value = gu[0];
    for (int i = 1; i < gu.size(); i++) {
      value = (value + gu[i]) / 2;
    }
    maxv = max(maxv, value);
  } while (next_permutation(gu.begin(), gu.end()));
  cout << maxv;
}
int main() {
  solve();
  return 0;
}
