#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, v;
  cin >> n;
  vector<double> a(n);
  double sum = 0;
  for (int i = 0; i < n; ++i) {
    cin >> v;
    a[i] = v;
  }
  sort(a.begin(), a.end());
  for (int j = 0; j < a.size(); ++j) {
    sum = (a[j] + a[j + 1]) / 2;
    a[j + 1] = sum;
  }
  cout << a[n - 1];
  return 0;
}
