#include<iostream>

#include<cstdio>

using namespace std;

long long n,L;

double a[1000001],b[1000001],sum[1000001];

int main()

{

    scanf("%lld%lld",&n,&L);

    for(long long i = 1;i <= n;i++)

    scanf("%lf",&a[i]);

    double eps = 1e-5;

    double l = -1e6,r = 1e6;

    while (r - l > eps)

    {

        double mid = (l + r) / 2;

        for(long long i = 1; i <= n; i++) b[i] = a[i] - mid;

        for(long long i = 1; i <= n; i++) sum[i] = sum[i - 1] + b[i];

        double ans = -1e10;

        double min_val = 1e10;

        for(long long 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;

}