#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<int> v;
  long double value = 0;
  int input;
  for (int i = 0; i < n; i++) {
    cin >> input;
    v.push_back(input);
  }
  sort(v.begin(), v.end());
  reverse(v.begin(), v.end());
  if (n > 2) {
    value += v[n - 1] * pow(0.5, n);
    for (int i = 1; i < n - 1; i++) {
      value += v[i] * pow(0.5, i + 1);
    }
  } else {
    value += v[1] * 0.5;
  }
  value += v[0] * 0.5;
  cout << value;
}
