#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  cin >> N;
  vector<double> V(N);
  for (int i = 0; i < N; i++) cin >> V.at(i);
  sort(V.begin(), V.end());
  int sum = V.at(0) / pow(2, N);
  for (int i = 0; i < N; i++) sum += V.at(i) / pow(2, N - i);
  cout << setprecision(8) << sum << endl;
  return 0;
}
