#include <bits/stdc++.h>
using namespace std;
int main() {
  int N, tmp = 1;
  double ans = 0;
  cin >> N;
  vector<double> v(N);
  for (int i = 0; i < N; i++) {
    cin >> v.at(i);
  }
  sort(v.begin(), v.end());
  reverse(v.begin(), v.end());
  for (int i = 0; i < N - 1; i++) {
    tmp *= 2;
    ans += v.at(i) / tmp;
  }
  ans += v.at(N - 1) / tmp;
  cout << ans << endl;
  return 0;
}
