#include <iostream>
using namespace std;
const int N = 1e6+10;
double a[N];
double sum[N];
int main()
{
    int N,L;
    cin>>N>>L;
    for(int i=1;i<=N;i++) cin>>a[i];
    double l = 1,r = 2000;
    while(r-l>1e-5)//r>l
    {
        double mid = (l+r)/2;
        for(int i=1;i<=N;i++) sum[i] = sum[i-1] + a[i] - mid;//前缀和，将avg>=mid ，转换为avg - mid >=0
        double ans = -1e10;
        double min_val = 1e10;
        for(int i=L;i<=N;i++)
        {
            min_val = min(min_val,sum[i-L]);
            ans = max(ans,sum[i] - min_val);
        }
        if(ans>=0) l = mid;
        else r= mid;
    }
    cout<<int(r*1000)<<endl;
    return 0;
}