#include <bits/stdc++.h>
using ld = long double;
int n, p;
std::priority_queue<int, std::vector<int>, std::greater<int>> q;
int main() {
  std::cin >> n;
  for (int i = 0; i < n; i++) {
    std::cin >> p;
    q.push(p);
  }
  while (q.size() > 1) {
    ld v1 = q.top();
    q.pop();
    ld v2 = q.top();
    q.pop();
    q.push((v1 + v2) / 2);
  }
  std::cout << q.top() << std::endl;
}
