#include<bits/stdc++.h>
using namespace std;

int main()
{
	int i, n;
	cin >> n;
	double a[n], ans;
	for(i=0; i<n; i+=1)
		cin >> a[i];
	sort(a, a+n);
	ans=(a[0]+a[1])/2;
	for(i=2; i<n; i+=1)
		ans=(ans+a[i])/2;
	cout << fixed << setprecision(10) << ans << endl;
}