#include <bits/stdc++.h>
int main() {
  int n;
  std::cin >> n;
  std::vector<double> v(n);
  for (auto&& vi : v) std::cin >> vi;
  std::sort(v.begin(), v.end());
  double sum = 0;
  for (auto&& vi : v) sum = (sum + vi) / 2;
  std::cout << sum << std::endl;
}
