#include <bits/stdc++.h>
using namespace std;
const double EPS = 1e-10;
const double PI = acos(-1.0);
inline int toInt(string s) {
  int v;
  istringstream sin(s);
  sin >> v;
  return v;
}
int main(void) {
  int n;
  scanf("%d", &n);
  vector<double> v(n);
  for (auto&& e : v) {
    scanf("%lf", &e);
  }
  sort((v).begin(), (v).end());
  double result = v.front();
  v.erase(v.begin());
  for (auto i = v.begin(); v.size() >= 2;) {
    if (*i * 2 >= i[1]) {
      result = (result + *i) / 2;
      v.erase(i);
    } else {
      result = (result + i[1]) / 2;
      v.erase(i + 1);
    }
  }
  result = (result + v[0]) / 2;
  printf("%lf\n", result);
  return 0;
}
