#include <stdio.h>
#include <math.h>
#define To2(x) (x)*(x)
#define MAXN 501
typedef struct
{	int x;
	int y;
}Point;
Point vex[MAXN];
double G[MAXN][MAXN],dis[MAXN];
int vexnum,visited[MAXN];
int S,P;
double fach(int i,int j)
{	
	return	(double)sqrt((double)(To2(vex[i].x-vex[j].x)+To2(vex[i].y-vex[j].y)));
}
void Initial(int N)
{	int i,j;
	for(i=1;i<=N;++i)
		for(j=1;j<=i;++j)
			G[i][j]=G[j][i]=fach(i,j);
	vexnum=N;
}
int FindMin()
{	int i,k=-1;
	double min=100000;
	for(i=1;i<=vexnum;++i)
	{	if(visited[i]==1)	continue;
		if(dis[i]<min)		k=i,min=dis[i];
	}
	return k;	
}
void qsort(int left,int right)
{	if(left<right)
	{	int i=left,j=right;
		double pivot=dis[left];
		while(i<j)
		{	while(i<j&&dis[j]>=pivot)	j--;
			if(i<j)		dis[i++]=dis[j];
			while(i<j&&dis[i]<pivot)	i++;
			if(i<j)		dis[j--]=dis[i];
		}
		dis[i]=pivot;
		qsort(left,i-1);
		qsort(i+1,right);
	}
}
void Prim(int k)
{	int i,j;
	for(i=1;i<=vexnum;++i)
		dis[i]=G[k][i],visited[i]=0;
	dis[k]=0,visited[k]=1;
	for(i=1;i<vexnum;++i)
	{	k=FindMin();
		if(k==-1)	break;
		visited[k]=1;
		for(j=1;j<=vexnum;++j)
		{	if(visited[j]==1)	continue;
			if(dis[j]>G[k][j])	dis[j]=G[k][j];	
		}
	}
	qsort(1,vexnum);
	printf("%.2lf\n",dis[vexnum-S+1]);
}
int main()
{	int N,i;
	scanf("%d",&N);
	while(N--)
	{	scanf("%d %d",&S,&P);
		for(i=1;i<=P;++i)
			scanf("%d %d",&vex[i].x,&vex[i].y);
		Initial(P);
		Prim(1);
	}
	return 0;
}