#include <iostream>
#include <iomanip>
#include <cstdio>
#include <queue>
#include <stack>
#include <cmath>
#define forn(i,n) for((i)=0;(i)<(n);(i)++)
#define MAXN 500

using namespace std;

int N,S,ROOT[MAXN];

struct edge{
    int n1,n2;
    float d;
};

struct point{
    int x,y;
};

bool operator < (const edge a, const edge b){
    return a.d>b.d;
}

vector <point> NODO;
priority_queue <edge> ARISTA;
stack <float> Q;

int findSet (int n){
    if(ROOT[n]==n)
        return n;
    return ROOT[n]=findSet(ROOT[n]);
}

bool isSameSet (int a, int b){
    return findSet(a)==findSet(b);
}

void unionSet (int a, int b){
    ROOT[findSet(b)]=ROOT[a];
}

float distancia (int a, int b){
    int x=NODO[a].x-NODO[b].x;
    int y=NODO[a].y-NODO[b].y;
    return sqrt(x*x+y*y);
}

int main()
{
    int testcases,kappa;
    int i,j,k;
    scanf("%i",&testcases);
    forn(kappa,testcases){
        scanf("%i %i",&S,&N);
        point naux;
        edge aaux;
        forn(i,N){
            scanf("%i %i",&j,&k);
            naux.x=j;   naux.y=k;
            NODO.push_back(naux);
        }
        forn(i,N){
            for(j=i+1;j<N;j++){
                aaux.d=distancia(i,j);  aaux.n1=i;  aaux.n2=j;
                ARISTA.push(aaux);
            }
        }

        forn(i,N)
            ROOT[i]=i;
        while(!ARISTA.empty()){
            aaux=ARISTA.top();
            ARISTA.pop();
            cout<<aaux.n1<<"\t"<<aaux.n2<<"\t"<<aaux.d<<endl;
            if(!isSameSet(aaux.n1,aaux.n2)){
                //cout<<aaux.n1<<"\t"<<aaux.n2<<"\t"<<aaux.d<<endl;
                unionSet(aaux.n1,aaux.n2);
                Q.push(aaux.d);
            }
        }

        S /= 2;
        while(!Q.empty() && S){
            Q.pop();
            S--;
        }
        if(Q.empty())
            printf("%.2f\n", 0);
            else
            printf("%.2f\n",Q.top());
        while(!Q.empty())
            Q.pop();

    }
    return 0;
}