#include <bits/stdc++.h>
using namespace std;
int N;
vector<int> v;
int main() {
  cin >> N;
  v = vector<int>(N);
  for (int i = 0; i < N; i++) {
    cin >> v.at(i);
  }
  double ans = 0.0;
  sort(v.begin(), v.end());
  int div = 1;
  for (int i = 0; i < N - 1; i++) {
    div *= 2;
  }
  ans = v.at(0) / (double)div;
  for (int i = 1; i < N; i++) {
    ans += v.at(i) / (double)div;
    div /= 2;
  }
  cout << fixed;
  cout << setprecision(10) << ans << endl;
  return 0;
}
