#include <bits/stdc++.h>
using namespace std;
int a[1000];
int main() {
  int n;
  cin >> n;
  for (int i = 0; i < n; i++) {
    scanf("%d", &a[i]);
  }
  sort(a, a + n);
  double num = (a[0] + a[1]) / 2;
  for (int i = 2; i < n; i++) {
    num += a[i];
    num /= 2;
  }
  cout << num << endl;
  return 0;
}
