#include<bits/stdc++.h>
const int maxn=1e5+1;
inline const void read(int &a)
{
	a=0;char c=getchar();
	while(c<'0'||c>'9')c=getchar();
	while(c>='0'&&c<='9')
	{
		a=a*10+c-'0';
		c=getchar();
	}
}
int n,k,d=0;
inline const bool comp(double a,double b)
{
	if(a>b)return true;
	return false;
}
int main()
{
	std::cin>>n>>k;
	int size[maxn],beauty[maxn];
	int sumsize[maxn],sumbeauty[maxn];
	double ans[50000];
	for(int i=1;i<=n;i++)read(size[i]);
	for(int i=1;i<=n;i++)read(beauty[i]);
	for(int i=1;i<=n;i++){sumsize[i]=sumsize[i-1]+size[i];sumbeauty[i]=sumbeauty[i-1]+beauty[i];}
	for(int i=1;i<=n;i++)
		for(int j=i;j<=n;j++)
		{
			ans[++d]=(double(sumsize[j]-sumsize[i-1]))/double((sumbeauty[j]-sumbeauty[i-1]));
			std::sort(ans+1,ans+1+d,comp);
		}
	printf("%.2lf ",ans[k]);
	return 0;
}