#include <bits/stdc++.h>
int main() {
  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());
  float accum = 0;
  float cache = (v[1] + v[0]) / 2.0f;
  accum = cache;
  for (int i = 2; i < n; i++) {
    float current = (v[i] + cache) / 2.0f;
    accum = current;
  }
  std::cout << accum << std::endl;
}
