#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  cin >> N;
  vector<int> vi(N);
  for (int i = 0; i < N; i++) {
    cin >> vi[i];
  }
  sort(vi.begin(), vi.end());
  double ans = 0;
  int div = 2;
  for (int i = N - 1; i > 0; i--) {
    ans += (double)vi[i] / (double)div;
    if (i != 1) div *= 2;
  }
  ans += (double)vi[0] / (double)div;
  cout << fixed << setprecision(6) << ans << endl;
  return 0;
}
