#include <bits/stdc++.h>
using namespace std;
int n, x, a, b;
double cnt;
priority_queue<double, vector<double>, greater<double> > pq;
int main(void) {
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> x;
    pq.push(x);
  }
  while (pq.size() > 1) {
    a = pq.top();
    pq.pop();
    b = pq.top();
    pq.pop();
    pq.push((a + b) / 2.0);
  }
  cout << pq.top() << endl;
  return 0;
}
