#include <bits/stdc++.h>
using namespace std;
int power(int x, int y) {
  for (int i = 0; i < y - 1; i++) {
    x *= x;
  }
  return x;
}
int main() {
  int n;
  cin >> n;
  vector<double> aji(n);
  for (int i = 0; i < n; i++) {
    cin >> aji.at(i);
  }
  sort(aji.begin(), aji.end());
  double sum = aji.at(0) / (double)power(2, n - 1);
  for (int i = 1; i < n; i++) {
    sum += aji.at(i) / (double)power(2, n - i);
  }
  cout << sum << endl;
}
