#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int hairetu[n];
  for (int i = 0; i < n; i++) {
    cin >> hairetu[i];
  }
  sort(hairetu, hairetu + (sizeof(hairetu) / sizeof(hairetu[0])));
  double temp = (hairetu[0] + hairetu[1]) / 2;
  for (int i = 2; i < n; i++) {
    temp = (temp + hairetu[i]) / 2;
  }
  cout << temp << endl;
}
