#include <fstream>
using namespace std;
int n, k;
int a[110000] = {0};
int sum[110000] = {0};
long double ans; 
long double pj(int i,int j);
int main()
{
    ifstream fin("helpz.in");
    ofstream fout("helpz.out");
    fin >> n >> k;
    for (int i = 1; i <= n; i++)
	{
        fin >> a[i];
        sum[i] = sum[i-1] + a[i];
    }
    int max = 0;
    for (int i = 0; i <= n-k; i++)
	{
        int j = i + k;
        if(pj(j, max) < pj(j, i))
		{
			max = i;
		}
        if(pj(j, max) > ans)
        {
			ans = pj(j, max);
		}
    }
    fout << (int)(ans*1000);
    return 0; 
}
long double pj(int i,int j)
{
	return (sum[i]-sum[j])/(long double)(i-j); 
}