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