#include <bits/stdc++.h>
using namespace std;
int a[51];
priority_queue<int, vector<int>, greater<int> > pq;
int main() {
  int n;
  cin >> n;
  for (int i = 1; i <= n; i++) {
    cin >> a[i];
    pq.push(a[i]);
  }
  if (n == 2) {
    cout << (double)(a[1] + a[2]) / 2.0;
    return 0;
  }
  n--;
  while (n--) {
    double t = (double)pq.top();
    pq.pop();
    t += (double)pq.top();
    pq.pop();
    pq.push(t / 2.0);
  }
  cout << (double)pq.top();
  return 0;
}
