#include <bits/stdc++.h>
using namespace std;
static const int MAX = 2e5 + 6;
int main() {
  int n;
  cin >> n;
  priority_queue<double, vector<double>, greater<double> > v;
  double a;
  for (int i = 0; i < n; i++) {
    cin >> a;
    v.push(a);
  }
  double p, q;
  while (!v.empty()) {
    p = v.top();
    v.pop();
    q = v.top();
    v.pop();
    v.push((p + q) / 2);
  }
  cout << v.top() << endl;
  return 0;
}
