# include <iostream>

 # include <cstdio>

 # include <cstring>

 # include <algorithm>

 # include <string>

 # include <cmath>

 # include <queue>

 # include <list>

 # define LL long long

 using namespace std ;

 struct point

 {

     int t ;

     int v ;

 }a[];

 bool cmp(point x , point y)

 {

     return x.t < y.t ;

 }

 int main()

 {

     //freopen("in.txt","r",stdin) ;

     int T ;

     scanf("%d" , &T) ;

     int Case =  ;

     while(T--)

     {

         int n , i ;

         Case++ ;

         double MAX =  ;

         scanf("%d" , &n) ;

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

            scanf("%d %d" , &a[i].t , &a[i].v) ;

         sort(a , a+n , cmp) ;

         for (i =  ; i < n- ; i++)

         {

             double ans = fabs((a[i+].v - a[i].v)*1.0/(a[i+].t - a[i].t)*1.0) ;

             if (ans > MAX)

                 MAX = ans ;

         }

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

     }

     return  ;

 }