# include <stdio.h>
# define q 32001
int a[q],b[q];
int n,p,u,i,x;
float f;
int main()
{
	freopen("secv3.in","r",stdin);
	freopen("secv3.out","w",stdout);
	scanf("%d%d%d",&n,&p,&u);
	for (i=1;i<=n;i++)
	{
		scanf("%d",&a[i]);
		a[i]=a[i]+a[i-1];
		if (i>p) a[i]-=a[i-p];
	}
	for (i=1;i<=n;i++)
		scanf("%d",&b[i]);
	x=1;
	for (i=2;i<=n;i++)
		if (a[x]*b[i]<b[x]*a[i]) x=i;
	f=(float)a[x]/b[x];
	printf("%.2f",f);
}