#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, i;
  double a, top1, top2, now, max;
  a = 0.0;
  top1 = 0.0;
  top2 = 0.0;
  now = 0.0;
  max = 0.0;
  cin >> n;
  priority_queue<int, vector<int>, greater<int> > que;
  for (i = 0; i < n; i++) {
    cin >> a;
    que.push(a);
  }
  for (i = 1; i < n; i++) {
    top1 = que.top();
    que.pop();
    top2 = que.top();
    que.pop();
    now = (top1 + top2) / 2.0;
    que.push(now);
    if (i == n - 1) {
      max = now;
    }
  }
  que.pop();
  cout << max << "\n";
  return (0);
}
