#include <iostream>

#include <cstring>

#include <cstdio>

#include <algorithm>

using namespace std;

struct node

{

    int t;

    int dis;

}pnode[100005];

bool cmp(node a,node b)

{

    return a.t < b.t;

}

int main()

{

    int T,n;

    scanf("%d",&T);

    int cas = 1;

    while(T--)

    {

        scanf("%d",&n);

        double ans = 0;

        for(int i = 0;i < n;i++)

        {

            scanf("%d%d",&pnode[i].t,&pnode[i].dis);

        }

        sort(pnode,pnode+n,cmp);

        for(int i = 1;i <= n;i++)

        {

            double tdis = (double)pnode[i].dis - pnode[i-1].dis;

            if(tdis < 0)

                tdis = -tdis;

            double tt = (double)pnode[i].t - pnode[i-1].t;

            ans = max(ans,tdis/tt);

        }

        printf("Case #%d: %.2lf\n",cas++,ans);

    }

    return 0;

}