#include <bits/stdc++.h>
using namespace std;
int a[55];
int main() {
  int n;
  cin >> n;
  for (int i = 0; i < n; i++) cin >> a[i];
  sort(a, a + n);
  double max = 0, s;
  do {
    s = a[0];
    for (int i = 0; i < n; i++) s = (s + a[i]) * 1.0 / (2 * 1.0);
    if (s > max) max = s;
  } while (next_permutation(a, a + n));
  cout << max;
}
