#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int main() {
  int n;
  cin >> n;
  vector<double> v(n);
  for (int i = 0; i < (n); i++) cin >> v[i];
  sort(v.begin(), v.end());
  double ans = 0;
  ans += v[0] / (1 << (n - 1));
  for (int i = 1; i < n; i++) {
    ans += v[i] / (1 << (n - i));
  }
  printf("%.10f\n", ans);
  return 0;
}
