#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  double ans = 0.0;
  cin >> n;
  vector<int> a(n), two(n, 1);
  for (int i = 0; i < n; i++) {
    cin >> a[i];
    if (i > 0) two[i] = 2 * two[i - 1];
  }
  sort(a.begin(), a.end());
  for (int i = 0; i < n; i++) {
    ans += (1.0 * a[i] * (i ? two[i - 1] : 1)) / (1.0 * two[n - 1]);
  }
  cout << ans << "\n";
  return 0;
}
