#include <bits/stdc++.h>
const long long MOD = 1e9 + 7;
const int MAX_N = 50;
int main() {
  int N;
  std::priority_queue<int> pq;
  std::cin >> N;
  for (int(i) = 0; i < (N); ++(i)) {
    int v;
    std::cin >> v;
    pq.push(-v);
  }
  double ans = 0.0;
  for (int(i) = 0; i < (N - 1); ++(i)) {
    int v1 = -pq.top();
    pq.pop();
    int v2 = -pq.top();
    pq.pop();
    ans = 0.5 * (v1 + v2);
    pq.push(-ans);
  }
  std::cout << std::fixed;
  std::cout << std::setprecision(10) << ans << '\n';
}
