#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  double ans = 0.0;
  cin >> n;
  vector<int> v(n);
  for (int i = 0; i < n; i++) {
    cin >> v.at(i);
  }
  sort(v.begin(), v.end());
  for (int i = 0; i < n - 1; i++) {
    if (i == 0)
      ans = (v.at(i) + v.at(i + 1)) / 2.0;
    else
      ans = (ans + v.at(i + 1)) / 2.0;
  }
  cout << ans << endl;
}
