#include<cstdio>
#include<cstring>
#define MAX(x,y) ((x)>(y)?(x):(y))
#define MIN(x,y) ((x)>(y)?(y):(x))
struct node
{
double x,y;
}q[100100];
double cal(double x1,double y1,double x2,double y2)
{
return (y1-y2)/(x1-x2);
}
double sum[100100];
int main()
{
int n,f;
scanf("%d%d",&n,&f);
memset(sum,0,sizeof(sum));
for(int i=1;i<=n;i++)
{
scanf("%lf",&sum[i]);
sum[i]+=sum[i-1];
}
q[0].x=0;q[0].y=0;
int head=0,tot=0;
double ans=-1;
for(int i=1;i<=n;i++)
{
while(head<=tot&&q[head].x+f<=i)
head++;
if(head>0)
{
ans=MAX(ans,(sum[i]-q[head-1].y)/(i-q[head-1].x));
}
while(head<tot&&cal(q[tot].x,q[tot].y,q[tot-1].x,q[tot-1].y)>cal(i,sum[i],q[tot].x,q[tot].y))
tot--;
q[++tot].x=i;
q[tot].y=sum[i];
}
printf("%d\n",(int)(ans*1000));
return 0;
}
