#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int *ar = new int[n];
  for (int i = 0; i < n; i++) cin >> ar[i];
  for (int i = n - 1; i > 0; i--) {
    for (int j = 0; j < i; j++) {
      if (ar[j] > ar[j + 1]) {
        int temp = ar[j];
        ar[j] = ar[j + 1];
        ar[j + 1] = temp;
      }
    }
  }
  float sum = (ar[0] + ar[1]) / 2.0;
  for (int i = 2; i < n - 1; i++) {
    sum = (sum + ar[i]) / 2.0;
  }
  cout << sum;
  return 0;
}
