#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<double> a(n);
  for (int i = 0; i < n; i++) {
    cin >> a[i];
  }
  sort(a.begin(), a.end());
  for (int i = n - 1; i >= 1; i--) {
    a[i - 1] = (a[i] + a[i - 1]) / 2.0;
  }
  cout << a[0];
  return 0;
}
