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