#include <bits/stdc++.h>
using namespace std;
const int N = 100010;
double ans[1000];
int main() {
  int n;
  cin >> n;
  for (int i = 1; i <= n; ++i) {
    cin >> ans[i];
  }
  sort(ans + 1, ans + n + 1);
  double sum = ans[1] + ans[2];
  int k = 2;
  for (int i = 3; i <= n; ++i) {
    sum += k * ans[i];
    k *= 2;
  }
  cout << fixed << setprecision(14) << (long double)sum / k;
}
