66666以红温66666

#include<bits/stdc++.h>
using namespace std;
double arr[300005];
int n,k;
bool jug(double mid)
{
	double mi = 0 ;
	for(int i = k ; i <= n ; i ++ )
	{
		if(arr[i] - i * mid > mi)return true;
		mi = min(mi,arr[i - k + 1] - (i - k + 1) * mid);
	}
	return false;
}

int main()
{

	cin >> n >> k ;
	for(int i = 1 ; i <= n ; i ++)
	{
		cin >> arr[i];
		arr[i] += arr[i-1];
	}
	
	double l = 0 ;
	double r = 1e6+10;
	while(r - l >= 0.0001)
	{
//		cout << r << " " << l << endl;
		double mid = (r + l) / 2;
		if(jug(mid)){
			l = mid;
		}else{
			r = mid;
		}
	}
	printf("%.4lf",l);
	
	return 0;
}