#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<int> value(n);
  for (int i = 0; i < n; i++) {
    cin >> value[i];
  }
  sort(value.begin(), value.end());
  double sum = (value[0] + value[1]) / 2;
  if (n > 2) {
    for (int i = 2; i < n; i++) {
      sum = (sum + value[i]) / 2;
    }
    cout << fixed << setprecision(10) << sum << endl;
  } else if (n == 2)
    cout << (value[0] + value[1]) / 2;
}
