#include<iostream>

#include<vector>

#include<algorithm>

#include<cstring>

#include<cstdio>

#include<cmath>

#include<cstdlib>

#include<ctime>

#include<queue>

#include<set>

#include<map>

#include<stack>

#include<bitset>

#include <iomanip>

#define rep(i,a,b) for(int i = a; i < b; i++)

#define _rep(i,a,b) for(int i = a; i <= b; i++)

#define mem(a,n) memset(a,n,sizeof(a))

#define fre(a) freopen(a,"r", stdin);

typedef long long LL;

using namespace std;

const double inf = 1e9;

int T,s,p;

double p2p(double x1, double y1, double x2, double y2){ //距离可以需要时候再求出来

    return sqrt((x1-x2) * (x1-x2) + (y1-y2)*(y1-y2));

}

double X[], Y[], dis[];

vector<int> G[];

bool vis[];

struct edge{

    int u ,v;

    double d;

    edge(int _u,int  _v, double _d):u(_u),v(_v),d (_d){};

};

bool cmp(edge a, edge b){

    return a.d > b.d;

}

void prim(){

    fill(dis, dis+, inf);

    mem(vis,);

    vis[] = ;

    dis[] = ;

    for(int i = ; i < G[].size(); i++){

        int v = G[][i];

        dis[v] = p2p(X[], Y[], X[v], Y[v]);

    }

    vector<double> ans;

    set<int> in;

    rep(times, , p-){

        double min_dis = 1e9;

        int pick = -;

        _rep(i,,p){

            if(!vis[i] && dis[i] < min_dis){

                min_dis = dis[i], pick = i;

            }

        }

        vis[pick] = ;

        ans.push_back(min_dis);

//        printf("min_dis : %.4f\n", min_dis);

        rep(i,,G[pick].size()){

            int v = G[pick][i];

            double d = p2p(X[pick], Y[pick], X[v], Y[v]);

            if(dis[v] > d) dis[v] = d;

        }

    }

    sort(ans.begin(), ans.end());

    if(s < ){//如果小于2， 那么不能减少任意一条边

        printf("%.2f\n", ans[ans.size() - ]);

        return;

    }

    if(p - s -  >= ans.size()) { //如果s - 1多于边的总数， 那么不用任何一条边

        puts("");

    }

    else printf("%.2f\n", ans[p-s-]); //找出第s-1大的边

}

int main(){

    cin >> T;

    while(T--){

        cin >> s >> p;

        _rep(i,,p){

            double x, y;

            cin >> x >> y;

            X[i] = x, Y[i] = y;

        }

        _rep(i,,p)_rep(j,i+,p){ //建一个完全图， 因为任意两点都是可达的

            G[i].push_back(j);

            G[j].push_back(i);

        }

        prim();

        _rep(i,,p) G[i].clear();

        mem(vis,);

        mem(X,);

        mem(Y,);

    }

    return ;

}