#include <bits/stdc++.h>
using namespace std;
int main() {
  int a[100], j, n, temp;
  double k;
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> a[i];
  }
  for (int i = 1; i < n; i++) {
    j = i;
    temp = a[i];
    while (j > 0 && temp < a[j - 1]) {
      a[j] = a[j - 1];
      j--;
    }
    a[j] = temp;
  }
  k = a[0];
  for (int i = 1; i < n; i++) {
    k = (k + a[i]) / 2;
  }
  cout << k;
  return 0;
}
