#include<bits/stdc++.h>
using namespace std;
int main() {
  int n;
  int a[] = new int[n + 1];
  cin >> n;
  ff(i, 1, n) cin >> a[i];
  sort(a + 1, a + 1 + n);
  double res = 0;
  ff(i, 2, n) a[i] = (a[i - 1] + a[i]) / 2;
  cout << res;
}