#define _USE_MATH_DEFINES
#include<iostream>
#include<vector>
#include<cstdio>
#include<string>
#include<algorithm>
#include <sstream>
#include<map>
#include<cmath>
#include<queue>
#include <functional>
#define rep(i,n) for (int i = 0; i < n; ++i)
#define PI 3.141592

using namespace std;

int main() {
	int N;
	cin >> N;

	//vector<int> vNum(N, 0);
	priority_queue<long double, vector<long double>, greater<long double> > vNum;

	rep(i, N)
	{
		long double tmp = 0;
		cin >> tmp;
		vNum.push(tmp);
	}

	while (true)
	{
		if (vNum.size() == 1)
		{
			break;
		}

		#define _USE_MATH_DEFINES
#include<iostream>
#include<vector>
#include<cstdio>
#include<string>
#include<algorithm>
#include <sstream>
#include<map>
#include<cmath>
#include<queue>
#include <functional>
#define rep(i,n) for (int i = 0; i < n; ++i)
#define PI 3.141592

using namespace std;

int main() {
	int N;
	cin >> N;

	priority_queue<long double, vector<long double>, greater<long double> > vNum;

	rep(i, N)
	{
		long double tmp = 0;
		cin >> tmp;
		vNum.push(tmp);
	}

	while (true)
	{
		if (vNum.size() == 1)
		{
			break;
		}

		long double AA = vNum.top();
		vNum.pop();
		long double BB = vNum.top();
		vNum.pop();

		vNum.push((AA + BB) / 2.0f);
	}


	printf("%.6f", vNum.top());
}
