#include <bits/stdc++.h>
using namespace std;
int main() {
  double n;
  cin >> n;
  priority_queue<double, vector<double>, greater<double> > pt;
  double a, b, sum = 0;
  for (int i = 0; i < n; i++) {
    scanf("%lf", &a);
    pt.push(a);
  }
  while (!pt.empty()) {
    a = pt.top();
    pt.pop();
    b = pt.top();
    pt.pop();
    sum = (a + b) / 2.0;
    pt.push(sum);
  }
  printf("%lf\n", sum);
  return 0;
}
