#include <stdio.h>
#include <stdlib.h>

#define N 50
}

int main() {
	static int v[N];
	int n;
	double p;
	scanf("%d", &n);
	for (int i = 0; i < n; i++)
		scanf("%d", &v[i]);
	p = v[0];
	for (i = 1; i < n; i++)
		p = (p+ v[i]) / 2;
	printf("%f\n", p);
	return 0;
}
