#include <bits/stdc++.h>
using namespace std;
const int N = 200005;
int main() {
  cout << fixed << setprecision(9);
  int n;
  cin >> n;
  int a[n];
  for (int i = 0; i < n; i++) {
    cin >> a[i];
  }
  sort(a, a + n);
  double sm = (a[0] + a[1]) / 2;
  for (int i = 2; i < n; i++) {
    sm = (sm + a[i]) / 2;
  }
  cout << sm;
  return 0;
}
