#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, a[10001];
  double cnt;
  cin >> n;
  for (int i = 0; i < n; i++) cin >> a[i];
  sort(a, a + n);
  cnt = a[1];
  for (int i = 1; i < n; i++) {
    cnt = (double)(cnt + a[i]) / 2;
  }
  cout << cnt << endl;
}
