#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());
  int sum = v[0] + v[1];
  for (int i = 2; i < n; ++i) {
    sum += pow(2, (i - 1)) * v[i];
  }
  double ans = (double)(sum);
  for (int i = 0; i < (n - 1); ++i) {
    ans /= 2;
  }
  cout << ans << endl;
  return 0;
}
