#include<bits/stdc++.h>

using namespace std;

int main() {
  int n, x;
  cin >> n;
  vector<int> data(n);
  priority_queue<int, vector<int>, greater<int> > pq;
  for (int i = 0; i < n; i++) {
    cin >> x;
    pq.push(x);
  }
  double res = 0;
  while (!pq.empty()) {
    x = pq.top();
    pq.pop();
    if (res == 0) {
      res = x;
    } else {
      res = (res + x) / 2; 
  }
  cout << res << endl;
  return 0;
}