#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  cin >> N;
  vector<double> V(N);
  for (int i = 0; i < (int)(N); i++) {
    cin >> V.at(i);
  }
  sort(V.begin(), V.end());
  double v = V.at(0);
  int k = 1, l = 1;
  for (int i = 0; i < (int)(N - 1); i++) {
    l *= 2;
  }
  for (int i = 1; i < N; i++) {
    v += k * V.at(i);
    k *= 2;
  }
  std::cout << std::setprecision(50) << v / l << endl;
}
