#include <bits/stdc++.h>
int main(void) {
  int N;
  std::cin >> N;
  std::vector<double> v(N);
  for (int i = 0; i < N; i++) {
    std::cin >> v[i];
  }
  for (int i = 0; i < N - 1; i++) {
    double val;
    std::sort(v.begin(), v.end());
    v.push_back((v[i] + v[i + 1]) / 2.0);
    v.erase(v.begin());
    v.erase(v.begin());
  }
  std::cout << v[0] << std::endl;
  return 0;
}
