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