#include <bits/stdc++.h>
int main() {
  int n;
  std::cin >> n;
  std::vector<float> v(n);
  for (int i = 0; i < n; i++) {
    std::cin >> v[i];
  }
  float accum = 0;
  bool flag = true;
  std::sort(v.begin(), v.end());
  while (flag) {
    int first = v.front();
    int second = v.at(1);
    accum = (first + second) / 2.0f;
    v.erase(v.begin());
    v.erase(v.begin());
    v.push_back(accum);
    std::sort(v.begin(), v.end());
    if (v.size() <= 1) {
      flag = false;
    }
  }
  std::cout << accum << std::endl;
}
