#include<fstream>
using namespace std;
ifstream fi("helpz.in");
ofstream fo("helpz.out");
int n,k,w[100001],a[100001],b[100001],S,mod,ans;
int main()
{
	fi>>n>>k;
	int i;
	for(i=1;i<=n;i++)fi>>w[i];
	S=0;
	for(i=1;i<=k;i++)S+=w[i];
	mod=k;
	a[k]=S;b[k]=k;
	for(i=k+1;i<=n;i++)
	{
		S=S-w[i-k]+w[i];
		a[i]=S;
		b[i]=k;
		if((a[i-1]+w[i])*1000/(b[i-1]+1)>S*1000/k)
		{
			a[i]=a[i-1]+w[i];
			b[i]=b[i-1]+1;
		}
	}
	ans=a[k]*1000/b[k];
	for(i=k+1;i<=n;i++)
	{
		if(a[i]*1000/b[i]>ans)
			ans=a[i]*1000/b[i];
	}
	fo<<ans<<endl;
	return 0;
}