/*****************************************
Problem Name  : 
******************************************/
#include <queue>
#include <math.h>
#include <stack>
#include <stdio.h>
#include <iostream>
#include <string.h>
#include <algorithm>
using namespace std;
#define LL long long
const int N = 1e5 + 10;
const double eps = 1e-5;
int n , m;
double a[N];
double g[N];
bool cheak(double x)
{
	g[0] = 0;
	for(int j = 1 ; j<= n; j++)
	    g[j] = a[j-1] - x + g[j-1];

	double minn = 0;
	for(int i = m , j = 0; i <= n ; j++,i++ )
	{
	    minn = min(g[j],minn);
		if(g[i] - minn >= 0)
			return true;
	}
	return false;
}
int main()
{
	cin >> n >> m;
	for(int i = 0 ; i< n ; i++)
		cin >> a[i];
	double l , r;
	l = 0 , r = 2000;
	while( r - l > eps)
	{
		double mid = (l + r) /2;
		if(cheak(mid))
			l = mid;
		else 
			r = mid;
	}
	cout << (int)(r*1000) <<  endl;
}