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