#include <bits/stdc++.h>
using namespace std;
const int N = 55;
int n;
int a[N];
int main() {
  cin >> n;
  for (int i = 1; i <= n; i++) {
    cin >> a[i];
  }
  double ans = 0;
  sort(a + 1, a + n + 1);
  for (int i = 1; i < n; i++) {
    ans = 1.0 * (a[i] + a[i + 1]) / 2;
    a[i + 1] = ans;
  }
  cout << setprecision(9) << fixed << ans << '\n';
  return 0;
}
