# include <stdio.h>
# define q 32001
int a[q],b[q],c[q],d[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]);
		d[i]=d[i-1]+a[i];
		if (i>p) d[i]-=a[i-p];
	}
	for (i=1;i<=n;i++)
	{
		scanf("%d",&b[i]);
		c[i]=c[i-1]+b[i];
		if (i>p) c[i]-=b[i-p];
	}
	x=p;
	for (i=p+1;i<=n;i++)
		if (d[x]*c[i]<c[x]*d[i]) x=i;
	f=(float)d[x]/c[x];
	printf("%.2f",f);
}