#include<cstdio>

#include<iostream>

#include<cstring>

#include<algorithm>

#define maxn 110000

#define INF 0x3f3f3f3f

using namespace std;

double list[maxn];

double s[maxn];

int f, n;

double l, r;

int check(double mid) {

	//获得前缀和

	for (int i = 1; i <= n; i++) {

		s[i] = list[i] - mid;

		s[i] += s[i - 1];

	}

	double mi = 1e8;

	double mx = -1e8;

	for (int i = f; i <= n; i++) {//1---n之间枚举

		mi = min(mi, s[i - f]);//get最小起点

		mx = max(mx, s[i] - mi);//get最大区间和

	}

	if (mx <= 0) {//mid不行，大了

		return 0;

	}

	else return 1;

	return 0;

}

int main() {

	scanf("%d %d", &n, &f);

	for (int i = 1; i <= n; i++) {

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

	}

	l = -1e6;

	r = 1e6;

	double mid;

	while(r-l>1e-5) {

		mid = (l + r) / 2;

		if (check(mid)) {//mid可以,答案还可以更大

			l = mid;

		}

		else {

			r = mid;

		}

	}

	printf("%d\n", (int)(r*1000));

	return 0;

}