#include <bits/stdc++.h>
using ll = long long;
using namespace std;
const auto mod = 1e9 + 7;
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(20);
  int n;
  cin >> n;
  vector<double> v(n);
  for (int i = 0; i < (int)(n); ++i) cin >> v[i];
  sort((v).begin(), (v).end());
  double ans = (v[0] + v[1]) / 2;
  if (n % 2 == 0) {
    for (int i = 3; i < (int)(n); ++i) ans = (ans + v[i]) / 2;
  } else {
    for (int i = 3; i < (int)(n - 1); ++i) ans = (ans + v[i]) / 2;
    ans = (ans + v[n - 1]) / 2;
  }
  cout << ans << endl;
}
