#include <bits/stdc++.h>
using namespace std;
const int N = 55;
int n, a[N];
double ans;
int main() {
  cin >> n;
  for (int i = 1; i <= n; i++) cin >> a[i];
  sort(a + 1, a + n + 1);
  ans = (a[1] + a[2]) / 2;
  for (int i = 3; i <= n; i++) ans = (ans + a[i]) / 2;
  cout << ans << endl;
  return 0;
}
