#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  cin >> N;
  vector<double> v(N);
  vector<int> P(N);
  double final_ans = 0;
  double T = 0;
  for (int i = 0; i < N; i++) {
    cin >> v.at(i);
    P.at(i) = i;
  }
  do {
    double cnt = v.at(P.at(0));
    for (int i = 1; i < N; i++) {
      cnt = (cnt + v.at(P.at(i))) / 2;
    }
    final_ans = max(cnt, T);
  } while (next_permutation(P.begin(), P.end()));
  cout << final_ans << endl;
}
