#pragma GCC optimize("Ofast")
#include<bits/stdc++.h>
#define LL long long
#define LLL __int128
#define uint unsigned
#define ldb long double
#define uLL unsigned long long
using namespace std;
const int N=1e6+5;
const ldb INF=1e10;
int n;ldb ans,D[N];pair<int,int>A[N];
inline ldb dist(const int&x,const int&y){
    const auto [xx,xy]=A[x];const auto [yx,yy]=A[y];
    return sqrtl(1ll*(xx-yx)*(xx-yx)+1ll*(xy-yy)*(xy-yy));
}
inline bool cmp(const pair<int,int>&x,const pair<int,int>&y){
    return x.second<y.second;
}
inline void solve(int l,int r){
    if(r-l<2){
        if(l<r&&!cmp(A[l],A[r]))swap(A[l],A[r]);
        return;
    }
    const int mid=(l+r)>>1;
    solve(l,mid),solve(mid+1,r);
    const int lx=max_element(A+l,A+mid+1)->first;
    const int rx=min_element(A+mid+1,A+r+1)->first;
    vector<int>S;
    for(int i=l,lp=mid+1,rp=mid+1;i<=mid;++i)
        if(rx-A[i].first<ans){
            for(;rp<=r&&A[rp].second-A[i].second<ans;++rp)
                if(A[rp].first-lx<ans)S.emplace_back(rp);
            for(;lp<rp&&A[i].second-A[lp].second>=ans;++lp);
            vector<int>T;T.reserve(10);
            for(auto j:S)if(j>=lp&&A[j].first-lx<ans)
                T.emplace_back(j),D[j]=dist(i,j);
            S=move(T),sort(S.begin(),S.end(),[&](const int&x,const int&y){return D[x]<D[y];});
            for(auto j:S)
                if(D[j]<ans)for(auto k:S)
                    if(k==j)break;
                    else ans=min(ans,(D[j]+D[k]+dist(j,k))/2);
                else break;
        }
    S.clear();
    for(int i=mid+1,lp=l,rp=l;i<=r;++i)
        if(A[i].first-lx<ans){
            for(;rp<=mid&&A[rp].second-A[i].second<ans;++rp)
                if(rx-A[rp].first<ans)S.emplace_back(rp);
            for(;lp<rp&&A[i].second-A[lp].second>=ans;++lp);
            vector<int>T;T.reserve(10);
            for(auto j:S)if(j>=lp&&rx-A[j].first<ans)
                T.emplace_back(j),D[j]=dist(i,j);
            S=move(T),sort(S.begin(),S.end(),[&](const int&x,const int&y){return D[x]<D[y];});
            for(auto j:S)
                if(D[j]<ans)for(auto k:S)
                    if(k==j)break;
                    else ans=min(ans,(D[j]+D[k]+dist(j,k))/2);
                else break;
        }
    inplace_merge(A+l,A+mid+1,A+r+1,cmp);
}
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),solve(1,n);
    cout<<fixed<<setprecision(12)<<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;
}