#include <bits/stdc++.h>
using namespace std;
int main(void) {
  int n;
  cin >> n;
  vector<double> v(n);
  for (int i = 0; i < (n); ++i) cin >> v[i];
  sort(v.begin(), v.end());
  reverse(v.begin(), v.end());
  double ans = 0;
  for (int i = 0; i < (n - 1); ++i) {
    double exp = (double)(1 << (i + 1));
    ans += v[i] / exp;
  }
  ans += v[n - 1] / (double)(1 << (n - 1));
  cout << ans << endl;
  return 0;
}
