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

int main(void)
{
	ios_base::sync_with_stdio(false);
	cin.tie(nullptr);

	int N = 0;
	cin >> N;
	vector<int> v(N);
	for (int i = 0; i < N; i++)
		cin >> v[i];

	sort(v.begin(), v.end());

	double price = 0;
	for (int i = 1; i < v.size(); i++)
	{
		int sum = 0;
		if (price == 0)
			sum = v[i - 1] + v[i];
		else
			sum = price + v[i];
		price = sum / 2.0;
	}

	cout << price << "\n";

	return 0;
