#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, tmp;
  priority_queue<int, vector<int>, greater<int> > queue;
  std::cin >> n;
  for (int i = 0; i < n; i++) {
    std::cin >> tmp;
    queue.push(tmp * 100000);
  }
  do {
    int now = 0;
    now += queue.top();
    queue.pop();
    now += queue.top();
    queue.pop();
    queue.push(now / 2);
  } while (queue.empty() != 1);
  printf("%5f\n", (double)queue.top() / 100000);
  return 0;
}
