#include "bits/stdc++.h"
// #define DEBUG
#ifdef DEBUG
#include "PrettyDebug.hpp"
#else
#define debug(...) [](){}()
#define debuga(...) [](){}()
#endif
#define For(i,a,b) for(int i=a;i<=b;i++)
#define Rev(i,a,b) for(int i=a;i>=b;i--)
#define Fin(file) freopen(file,"r",stdin)
#define Fout(file) freopen(file,"w",stdout)
using namespace std; typedef long long ll;
namespace FastIO{
    const int BUF_SIZ=1<<16;
    char in_buf[BUF_SIZ],*got_pos=in_buf,*read_pos=in_buf,out_buf[BUF_SIZ],*write_pos=out_buf;
    inline char get_next_char(){if(read_pos==got_pos){got_pos=read_pos=in_buf;got_pos+=fread(got_pos,sizeof(char),BUF_SIZ,stdin);}return*(read_pos++);}
    inline void flush_output(){fwrite(out_buf,sizeof(char),write_pos-out_buf,stdout);write_pos=out_buf;}
    inline void put_char(char ch){*(write_pos++)=ch;if(write_pos==out_buf+BUF_SIZ)flush_output();}
#define FASTIO_READ_NEGATIVE
#ifndef FASTIO_READ_NEGATIVE
    template<typename T> inline void read(T& res){char ch;while(!isdigit(ch=get_next_char()));res=ch^'0';while(isdigit(ch=get_next_char()))res=(res<<3)+(res<<1)+(ch^'0');}
#else
    template<typename T> inline void read(T& res){char ch;bool flg=0;while(!isdigit(ch=get_next_char()))flg|=ch=='-';res=ch^'0';while(isdigit(ch=get_next_char()))res=(res<<3)+(res<<1)+(ch^'0');if(flg)res=-res;}
#endif
    template<typename T> inline void write(T x){if(!x){put_char('0');return;}static int lis[25],*lp=lis;while(x){*(++lp)=x%10;x/=10;}while(lp!=lis)put_char((*(lp--))+'0');}
    template<typename T> inline void writeln(const T& x){write(x);put_char('\n');}
    template<typename T> inline void writesp(const T& x){write(x);put_char(' ');}
    class _IO_Flusher{public:~_IO_Flusher(){flush_output();}}__Flusher;
    class IStream{public:
        template<typename T> inline IStream& operator>>(T& x){read(x);return *this;}
        inline IStream& operator>>(char* str){char ch;while(isspace(ch=get_next_char()));(*(str++))=ch;while(!isspace(ch=get_next_char())){if(ch==EOF)break;(*(str++))=ch;}*str=0;return *this;}
    }Cin;
    class OStream{public:
        template<typename T> inline enable_if_t<is_integral<T>::value,OStream&> operator<< (const T& x){write(x);return *this;}
        inline OStream& operator<< (const char& ch){put_char(ch);return *this;}
        inline OStream& operator<< (const char* str){for(const char* p=str;*p;put_char(*(p++)));return *this;}
    }Cout;
}
using namespace FastIO;
#define cin Cin
// #define cout Cout
mt19937 rng(19031253);
template<typename _Key,typename _Val,int N>
class HashTable{
    static constexpr int mod = 1e6+7;
    int head[mod],nxt[N],tot,vis[mod],V; _Val val[N]; _Key key[N];
    inline int hash(_Key k) { int res=k%mod; res=(res+mod)%mod; return res; }
public:
    void clear() { tot=0; V++; }
    bool count(_Key k){
        int h=hash(k); if(vis[h]!=V) vis[h]=V,head[h]=0;
        int u=head[h]; while(u&&key[u]!=k) u=nxt[u];
        return u!=0;
    }
    _Val& operator[] (_Key k){
        int h=hash(k); if(vis[h]!=V) vis[h]=V,head[h]=0;
        int u=head[h]; while(u&&key[u]!=k) u=nxt[u];
        if(!u){
            nxt[++tot]=head[h]; val[tot]=0; head[h]=tot; key[tot]=k; return val[tot];
        }
        else return val[u];
    }
};
constexpr int N=2e6+5;
HashTable<ll,int,N*2> O;
// map<ll,int> O;
int n,tmp[N],lis[N][20],lcnt[N],tot; double X[N],Y[N];
inline double dist(int u,int v) { return sqrt((X[u]-X[v])*(X[u]-X[v])+(Y[u]-Y[v])*(Y[u]-Y[v])); }
signed main(){
    // Fin("data.in"); //Fout("triangle.out");
    // Fin("triangle2.in");
    atexit([](){cerr<<"Time = "<<clock()<<" ms"<<endl;});
    int T; cin>>T; while(T--){
        cin>>n; double theta=uniform_real_distribution<double>(0,2*acos(-1.0))(rng), cost=cos(theta), sint=sin(theta);
        For(i,1,n){
            int x,y; cin>>x>>y; X[i]=x; Y[i]=y;
            X[i]=x*cost-y*sint;
            Y[i]=x*sint+y*cost;
        }
        iota(tmp+1,tmp+1+n,1); shuffle(tmp+1,tmp+1+n,rng); tot=0; O.clear();
        double ans=3e9;
        For(_,1,n){
            int u=tmp[_]; ll x=X[u]/ans/2,y=Y[u]/ans/2;
            int hh[200]={0},hcnt=0;
            For(dx,-1,1) For(dy,-1,1){
                ll qwq=(x+dx)*ll(2e9)+(y+dy);
                if(O.count(qwq)){
                    int o=O[qwq]; For(i,0,lcnt[o]-1) assert(hcnt!=199),hh[++hcnt]=lis[o][i];
                }
            }
            assert(hcnt<150);
            double res=4e9;
            For(i,1,hcnt) For(j,i+1,hcnt){
                res=min(res,dist(u,hh[i])+dist(u,hh[j])+dist(hh[i],hh[j]));
                if(abs(res)<1e-8) { cout<<"0\n"; exit(0); }
            }
            if(res<ans){
                debug("remake",_);
                ans=res; O.clear(); tot=0;
                For(i,1,_){
                    int v=tmp[i]; ll x0=X[v]/ans/2, y0=Y[v]/ans/2;
                    ll qwq=x0*ll(2e9)+y0;
                    int& o=O[qwq]; if(o==0) lcnt[o=++tot]=0;
                    // assert(lcnt[o]!=10);
                    lis[o][lcnt[o]++]=v;
                }
            }
            else{
                ll qwq=x*ll(2e9)+y;
                int& o=O[qwq]; if(o==0) lcnt[o=++tot]=0;
                lis[o][lcnt[o]++]=u;
            }
        }
        // cout<<setprecision(10)<<fixed<<ans<<'\n';
        static int kase=0;
        cout<<"Case #"<<++kase<<": "<<setprecision(10)<<fixed<<ans<<'\n';
    }
    return 0;
}

// CONTINUE, NON-STOPPING, FOR CHARLIEY
// START TYPING IF YOU DON'T KNOW WHAT TO DO
// STOP TYPING IF YOU DON'T KNOW WHAT YOU'RE DOING

// Started Coding On: April 11 Thu, 08 : 08 : 12