#include<bits/stdc++.h>
using namespace std;
const int N=510;
struct edge{int x,y;double c;}e[N*N],s[N];int elen;
int n,m,fa[N];
double dist(int X1,int Y1,int X2,int Y2)
{
    double x=(double)(X1-X2);
    double y=(double)(Y1-Y2);
    return sqrt(x*x+y*y);
}
bool cmp(edge n1,edge n2){return n1.c<n2.c;}
int findfa(int x){return fa[x]==x?x:fa[x]=findfa(fa[x]);}
double kruskal()
{
    sort(e+1,e+1+elen,cmp);
    for(int i=1;i<=n;i++)fa[i]=i;
    int t=0;double ans=0;
    for(int i=1;i<=elen;i++)
	{
        int tx=findfa(e[i].x),ty=findfa(e[i].y);
        if(tx!=ty)
		{
            fa[tx]=ty;
            if(++t==n-1-(m-1))
			{
                ans=e[i].c;
                break;
            }
        }
    }
    return ans;
}
int main()
{

        scanf("%d%d",&m,&n);elen=0;
        for(int i=1;i<=n;i++)scanf("%d%d",&s[i].x,&s[i].y);
        for(int i=1;i<=n;i++)    
            for(int j=i+1;j<=n;j++)
			{
                double d=dist(s[i].x,s[i].y,s[j].x,s[j].y);
                e[++elen]={i,j,d};
            }
        printf("%.2f\n",kruskal());
 
    return 0;
}