#include <bits/stdc++.h>
using namespace std;
int32_t main() {
  long long int n;
  cin >> n;
  long long int a[n + 5];
  for (long long int i = 1; i <= n; i++) cin >> a[i];
  sort(a + 1, a + 1 + n);
  double ans = (a[1] + a[2]) / 2;
  for (long long int i = 3; i <= n; i++) ans = (ans + a[i]) / 2;
  cout << fixed << setprecision(10) << ans;
}
