#include <bits/stdc++.h>
int main() {
  int n;
  std::priority_queue<double, std::vector<double>, std::greater<double> > q;
  std::cin >> n;
  for (int i = 0; i < n; i++) {
    int v;
    std::cin >> v;
    q.push((double)v);
  }
  while (q.size() > 1) {
    double a, b;
    a = q.top();
    q.pop();
    b = q.top();
    q.pop();
    q.push((a + b) / 2);
  }
  double r = q.top();
  std::cout << std::setprecision(5) << r << std::endl;
}
