#include <stdio.h>
#include <stdlib.h>
#DEFINE N 50

  static int compare (void const *a, void const *b)
{

   int const *pa = a;
   int const *pb = b;
   return *pa - *pb;

}

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