#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, v[10000];
  cin >> n;
  float ans = 0;
  for (int i = 0; i < n; ++i) {
    cin >> v[i];
  }
  sort(v, v + n);
  int temp = pow(2, n - 1);
  for (int i = 0; i < n; ++i) {
    if (i < 2)
      ans += v[i] / temp;
    else
      ans += pow(2, i - 1) * v[i] / temp;
  }
  cout << ans << endl;
}
