#include <bits/stdc++.h>
using namespace std;
int main(void) {
  int N;
  std::cin >> N;
  std::vector<int> v(N);
  for (int i = 0; i < N; i++) {
    std::cin >> v[i];
  }
  std::sort(v.begin(), v.end());
  double results = 0.0;
  for (int i = 0; i < N; i++) {
    results = (results + v[i]) / 2;
  }
  std::cout << std::fixed << std::setprecision(5) << results << std::endl;
}
