#include<cstdio>
#include<algorithm>
using namespace std;
int a[100005];
int main() {
int n;
scanf("%d",&n);
for (int i = 0; i < n; i++) 
scanf("%d",&a[i]);
double sum = 0;
sort(a,a+n);
sum += a[n/2];
sum += a[n-1-n/2];
printf("%.10f\n", sum/2);
return 0;
}