#include <bits/stdc++.h>
using namespace std;
int a[100005];
int main() {
  int n;
  cin >> n;
  for (int i = 0; i < n; i++) cin >> a[i];
  sort(a, a + n);
  stack<long double> q;
  for (int i = n - 1; i >= 0; i--) {
    q.push(a[i]);
  }
  while (q.size() != 1) {
    int x = q.top();
    q.pop();
    int y = q.top();
    q.pop();
    q.push((x + y) * 1.0 / 2);
  }
  cout << q.top();
}
