#include <bits/stdc++.h>
using namespace std;
int n;
priority_queue<double> pq;
int main() {
  cin >> n;
  for (int i = 0; i < n; i++) {
    int t;
    cin >> t;
    pq.push(-t * 1.0);
  }
  while (pq.size() > 1) {
    double a = -pq.top();
    pq.pop();
    double b = -pq.top();
    pq.pop();
    pq.push(-(a + b) / 2);
  }
  cout << fixed << setprecision(10) << -pq.top();
  return 0;
}
