#include<bits/stdc++.h>
#include<iostream>
#include<algorithm>
#define ll long long
using namespace std;
const int Inf=1e5+1;
int  n,l;
ll sum[Inf];
ll a[Inf];
void Int(){
	scanf("%d%d",&n,&l);
	for(int i=1;i<=n;i++)
	{
		scanf("%lld",&a[i]);
		a[i]*=1000;
		sum[i]=sum[i-1]+a[i];
	}
	ll ans=0;
	for(int i=l;i<=n;i++){
		ans=max(ans,(sum[i]-sum[i-l])/l);
	}
	printf("%lld",ans);
}
signed main(){
    int t=1;
    while(t--)Int();
	return 0;
}