#include <iostream>
using namespace std;

void bsort(double a[], int n)
{
	for (int i = 0; i < n - 1; i++) {
		for (int j = n - 1; j > i; j--) {
			if (a[j - 1] > a[j]) {
				int temp = a[j];
				a[j] = a[j - 1];
				a[j - 1] = temp;
			}
		}
	}
}

int main()
{
	int N = 0;
	double v[1000] = { 0 };
	double res = 0;

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

	bsort(v, N);

	res += v[0] / pow(2, N - 1);
	for (int i = 1; i < N; i++) {
		res += v[i] / pow(2, N - i);
	}
	
	cout << res;

	return 0;
}

