#include <bits/stdc++.h>
using namespace std;
priority_queue<float, vector<float>, greater<float> > q;
int n;
float x;
int main() {
  cin >> n;
  for (int i = 1; i <= n; i++) cin >> x, q.push(x);
  for (int i = 1; i < n; i++) {
    int a = q.top();
    q.pop();
    int b = q.top();
    q.pop();
    q.push((float)(a + b) / 2);
  }
  cout << q.top();
  return 0;
}
