#include <bits/stdc++.h>
using namespace std;
double a[10000];
int n;
double ans = 0;
double cnt() {
  double las = a[1];
  for (int i = 2; i <= n; i++) {
    las = (a[i] + las) / 2;
  }
  return las;
}
int main() {
  cin >> n;
  for (int i = 1; i <= n; i++) cin >> a[i];
  sort(a + 1, a + n + 1);
  do {
    ans = max(ans, cnt());
  } while (next_permutation(a + 1, a + n + 1));
  cout << ans;
  return 0;
}
