#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  while (cin >> N) {
    vector<double> vs;
    for (int i = 0; i < N; ++i) {
      double v;
      cin >> v;
      vs.push_back(v);
    }
    sort(vs.begin(), vs.end());
    int k = 1;
    double ans = 0;
    for (int i = N - 1; i >= 0; --i) {
      if (i != 0) k *= 2;
      ans += vs[i] / k;
    }
    printf("%0.8f\n", ans);
  }
}
