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