#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  float a[51], ans = 0;
  cin >> n;
  for (int i = 1; i <= n; i++) cin >> a[i];
  sort(a, a + n + 1);
  for (int i = 1; i < n; i++) a[i + 1] = (a[i] + a[i + 1]) / 2;
  cout << a[n];
  return 0;
}
