#include <bits/stdc++.h>
using namespace std;
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  int n;
  cin >> n;
  double v;
  vector<double> vv(n);
  for (int i = 0; i < n; i++) cin >> vv[i];
  sort(vv.begin(), vv.end());
  int m = 1;
  double s = vv[0];
  for (int i = 1; i < n; i++) {
    s += (double)m * vv[i];
    m *= 2;
  }
  cout << setprecision(20) << s / m << endl;
  return 0;
}
