#include <iostream>
#include <cstdio>
#include <stdlib.h>
using namespace std;
int n, k, weight[100000], sum= 0;
int ans;

inline int comp(const void*a,const void*b)
{
	return*(int*)b-*(int*)a;
}

int main()
{
	freopen("helpz.in","r",stdin);
	freopen("helpz.out","w",stdout);
	cin >>n >>k;
	int i;
	for(i = 1;i <= n;i++)
	{
		scanf("%d",&weight[i]);
	}
	qsort(weight+1, i, sizeof(int), comp);
	for(i=1;i<=k;i++)
		sum += weight[i];
	
	ans = (((double)sum / k )* 1000);
	cout << ans;
	return 0;
}