#include<bits/stdc++.h>
using namespace std;
const int N=1000010;
struct s{
	int x,y;
	bool operator<(s b){
		return x<b.x;
	}
}p[N],x[N],y[N];
double dist(s a,s b){
	return sqrt(1ll*(a.x-b.x)*(a.x-b.x)+1ll*(a.y-b.y)*(a.y-b.y));
}
double solve(int l,int r){
	int mid=(l+r)>>1,cntx=0,cnty=0,posl=1,posr=1;
	double px=(p[mid].x+p[mid+1].x)/2.0,delta,ans;
	if(l==r){
		return 1e18;
	}
	ans=delta=min(solve(l,mid),solve(mid+1,r));
	for(int i=l;i<=mid;i++){
		if(px-p[i].x<=delta/2){
			x[++cntx]=p[i];
		}
	}
	for(int i=mid+1;i<=r;i++){
		if(p[i].x-px<=delta/2){
			y[++cnty]=p[i];
		}
	}
	sort(x+1,x+cntx+1,[](s a,s b){return a.y<b.y;});
	sort(y+1,y+cnty+1,[](s a,s b){return a.y<b.y;});
	for(int i=1;i<=cntx;i++){
		while(posl<=cnty&&x[i].y-y[posl].y>delta/2){
			posl++;
		}
		while(posr+1<=cnty&&y[posr+1].y-x[i].y<=delta/2){
			posr++;
		}
		for(int j=posl;j<=posr;j++){
			for(int k=j+1;k<=posr;k++){
				ans=min(ans,dist(x[i],y[j])+dist(x[i],y[k])+dist(y[j],y[k]));
			}
		}
	}
	return ans;
}
int main(){
	int t,n;
	scanf("%d",&t);
	for(int tt=1;tt<=t;tt++){
		scanf("%d",&n);
		for(int i=1;i<=n;i++){
			scanf("%d%d",&p[i].x,&p[i].y);
		}
		sort(p+1,p+n+1);
		printf("Case #%d: %.6lf\n",tt,solve(1,n));
	}
}