#include<stdio.h>
#include<string.h>
#include<algorithm>
#include<math.h>
#define MAX 10100
#define DD double
using namespace std;
struct node
{
	int time,pos;
}s[MAX];
bool cmp(node a,node b)
{
	return a.time<b.time;
}
int main()
{
	int t,n,m,i,j,k;
	scanf("%d",&t);
	k=0;
	while(t--)
	{
		scanf("%d",&n);
		DD sum=0,ans=0;
		for(i=0;i<n;i++)
		    scanf("%d%d",&s[i].time,&s[i].pos);
		sort(s,s+n,cmp);
		for(i=0;i<n-1;i++)
		{		
		    DD sum=(s[i+1].pos-s[i].pos)*1.0/(s[i+1].time-s[i].time);
			ans=max(fabs(sum),ans);
		}
		printf("Case #%d: %.2lf\n",++k,ans);
	}
	return 0;
}