#include <bits/stdc++.h>
using namespace std;
int main() {
  double n, sum = 0;
  cin >> n;
  vector<long long> v(n);
  for (int i = 0; i < (n); ++i) cin >> v[i];
  sort(v.begin(), v.end());
  for (long long i = 0; i < n; i++) {
    if (i == 0 || i == 1)
      sum += v[i] * pow(0.5, n - 1);
    else
      sum += v[i] * pow(0.5, i - 1);
  }
  cout << fixed << setprecision(10) << sum << endl;
}
