#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  double v[50];
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> v[i];
  }
  sort(v, v + n);
  double ans = 0;
  ans = (v[0] + v[1]) / 2;
  for (int i = 2; i < n; i++) {
    ans = (v[i] + ans) / 2;
    i++;
  }
  cout << ans << endl;
  return 0;
}
