#include<bits/stdc++.h>
#define LL long long
#define LLL __int128
#define uint unsigned
#define ldb double
#define uLL unsigned long long
using namespace std;
const int N=1e6+5;
const ldb INF=1e10;
int n;ldb ans;pair<int,int>A[N];
inline ldb dist(const pair<int,int>&x,const pair<int,int>&y){
    const auto [xx,xy]=x;const auto [yx,yy]=y;
    return sqrt(1ll*(xx-yx)*(xx-yx)+1ll*(xy-yy)*(xy-yy));
}
inline void MAIN(){
    cin>>n,ans=INF;
    for(int i=1;i<=n;++i)
        cin>>A[i].first>>A[i].second;
    sort(A+1,A+n+1);
    multiset<pair<int,int>>S;
    for(int i=1;i<=n;++i)swap(A[i].first,A[i].second);
    for(int i=1,j=1;i<=n;++i){
        for(;A[i].second-A[j].second>=ans;S.erase(S.find(A[j++])));
        const auto tl=S.lower_bound(make_pair((int)max(-1e9,floor(A[i].first-ans)),0));
        const auto tr=S.lower_bound(make_pair((int)min(1e9,ceil(A[i].first+ans)),0));
        for(auto a=tl;a!=tr;++a)for(auto b=tl;b!=a;++b)ans=min(ans,(dist(A[i],*a)+dist(A[i],*b)+dist(*a,*b))/2);
        S.emplace(A[i]);
    }
    cout<<fixed<<setprecision(9)<<ans*2<<'\n';
}
signed main(){
    cin.tie(0)->sync_with_stdio(0);
    int t=1;cin>>t;for(int _=1;t--;++_)
        cout<<"Case #"<<_<<": ",MAIN();
    return 0;
}