#include <bits/stdc++.h>
int main() {
  long long n;
  std::cin >> n;
  std::vector<double> v(n);
  for (long long i = 0; i < n; i++) {
    std::cin >> v[i];
  }
  std::sort(v.begin(), v.end());
  long long num = n;
  while (num != 1) {
    std::vector<double> v2;
    for (long long i = 0; i + 1 < num; i += 2) {
      v2.push_back((v[i] + v[i + 1]) / 2.0);
    }
    if (v.size() % 2 == 1) {
      v2.push_back(v.back());
    }
    num = (num + 1) / 2;
    v = v2;
  }
  std::cout << v[0] << std::endl;
  return 0;
}
