#include <bits/stdc++.h>
using namespace std;
int n, a[200012];
void input() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  cin >> n;
  for (int i = 1; i <= n; i++) {
    cin >> a[i];
  }
  sort(a + 1, a + 1 + n, greater<int>());
  int dem = 2;
  double res = 0;
  for (int i = 1; i <= n - 1; i++) {
    res += (double)a[i] / dem;
    dem *= 2;
  }
  res += (double)a[n] / dem * 2;
  cout << res;
}
int main() {
  input();
  return 0;
}
