#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 = 0; i < N - 1; i++) {
    a[i + 1] = (a[i] + a[i + 1]) / 2;
  }
  cout << a[N - 1] << endl;
}
