#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<int> v;
  for (int i = 0; i < n; i++) {
    int a;
    cin >> a;
    v.push_back(a);
  }
  if (n == 2) {
    double a = v[0] + v[1];
    a /= 2;
    cout << a << endl;
    return 0;
  }
  sort(v.rbegin(), v.rend());
  double ans = v[2];
  for (int i = 1; i >= 0; i--) {
    ans += v[i];
    ans /= 2;
  }
  cout << ans << endl;
}
