#include <bits/stdc++.h>
using namespace std;
int n;
int main() {
  priority_queue<double> pq;
  cin >> n;
  for (int i = 0; i < n; i++) {
    double x;
    cin >> x;
    pq.push(x);
  }
  while (pq.size() > 1) {
    double x = pq.top();
    pq.pop();
    double y = pq.top();
    pq.pop();
    pq.push((x + y) / 2);
  }
  printf("%lf\n", pq.top());
  return 0;
}
