#include <bits/stdc++.h>
using namespace std;
long long gcd(long long a, long long b) { return b ? gcd(b, a % b) : a; }
long long lcm(long long a, long long b) { return a / gcd(a, b) * b; }
int main() {
  int n;
  cin >> n;
  double ans = 0;
  int data[50];
  for (int i = 0; i < (int)(n); i++) {
    cin >> data[i];
  }
  sort(data, data + n);
  for (int i = 0; i < n - 1; i++) {
    ans = (double)((double)data[i] + (double)data[i + 1]) / (double)2.0;
    data[i + 1] = ans;
    sort(data + i + 1, data + n);
  }
  cout << fixed << setprecision(20) << ans << endl;
}
