#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int n;
  cin >> n;
  vector<int> v(n);
  for (int i = 0; i < n; ++i) {
    cin >> v[i];
  }
  sort(v.rbegin(), v.rend());
  float value = 0;
  for (int i = 1; i <= n; ++i) {
    if (i != n) {
      value += (float)(v[i - 1]) / (1 << i);
    } else {
      value += (float)(v[n - 1]) / (1 << (n - 1));
    }
  }
  cout << value << "\n";
  return 0;
}
