#include <bits/stdc++.h>
using namespace std;
int main(int argc, char *argv[]) {
  int n;
  vector<double> v(50);
  double ans = 0.0;
  cin >> n;
  for (int i = 0; i < n; i++) cin >> v[i];
  sort(v.begin(), v.end(), greater<double>());
  for (int i = 0; i < n; i++) {
    ans += v[i] / pow(2.0, (double)i + 1.0);
  }
  cout << ans << endl;
  return 0;
}
