#include <bits/stdc++.h>
using namespace std;
int N;
vector<double> v;
int main() {
  cin >> N;
  v = vector<double>(N);
  for (int i = 0; i < N; i++) {
    cin >> v[i];
  }
  vector<int> perm(N);
  for (int i = 0; i < N; i++) {
    perm[i] = i + 1;
  }
  double ans = 0;
  do {
    double ans1 = v[perm[0] - 1];
    for (int i = 1; i < N; i++) {
      ans1 = (ans1 + v[perm[i] - 1]) / 2;
    }
    ans = max(ans, ans1);
  } while (next_permutation(perm.begin(), perm.end()));
  cout << fixed << setprecision(12) << ans << endl;
}
