#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];
  }
  while (1) {
    std::vector<double> buf;
    std::sort(v.begin(), v.end());
    for (int i = 0; i < v.size(); i += 2) {
      if (i == N - 1) {
        buf.push_back(static_cast<double>(v[i]));
      } else
        buf.push_back(
            (static_cast<double>(v[i]) + static_cast<double>(v[i + 1])) / 2.0);
    }
    v.clear();
    std::copy(buf.begin(), buf.end(), std::back_inserter(v));
    if (v.size() == 1) break;
  }
  std::cout << v[0] << std::endl;
  return 0;
}
