#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <math.h>
#include <string.h>
int cmp(const void *a, const void *b)
{
	return *(unsigned int*)a - *(unsigned int *)b;
}
int main()
{
	unsigned int i,n;
	unsigned int s[250001];
	scanf("%u",&n);
	for(i=0;i<n;i++)
		scanf("%u",s+i);
	qsort(s,n,sizeof(unsigned int),cmp);
	double res=(double)s[n/2]+(double)s[(n-1)/2];
	printf("%.1llf",res/2.0);
	return 0;
}