#include<iostream>
#include<algorithm>

int main() {
	int n;
	std::cin >> n;
	double *v = new double[n];
	for (int i = 0; i < n; i++)std::cin >> v[i];
	std::sort(v, &v[n]);
	for (int i = 1; i < n; i++) {
		v[0] = (v[0] + v[i]) / 2;
	}
	printf("%lf\n", v[0]);
}