#include<iostream>
#include<cstdio>
#include<queue>
using namespace std;
priority_queue<double,vector<int>,greater<int> > q;
int main(void)
{
	int n;
	double m;
	double ans = 0;
	scanf("%d",&n);
	for(int i = 1;i<=n;i++) 
	{
		scanf("%lf",&m);
		q.push(m);
	}
	while(q.size()!=1)
	{
		double a = q.top();
		q.pop();
		double b = q.top();
		q.pop();
		ans = (double)(a+b)*0.5;
//		cout<<ans<<endl;
		q.push(ans);
	}
	printf("%.1lf",ans);
	return 0;
} 