#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());
  double ans = 0;
  int D = 1;
  for (int i = N - 1; i >= 0; i--) {
    if (i != 0) {
      D *= 2;
    }
    ans += (double)v[i] / D;
  }
  cout << fixed << setprecision(1) << ans << endl;
}
