#include <bits/stdc++.h>
using namespace std;
int xx[1005],yy[1005],s,p;
int i,j,f[1000005],total=0,alnum=0;
double ans;
struct point
{
double x,y,v;
}a[1000005];
bool cmp(point a,point b)
{
return a.v<b.v;
}
int father(int p)
{
if(f[p]==p) return p;
return father(f[p]);
}
using namespace std;
int xx[1005],yy[1005],s,p;
int i,j,f[1000005],total=0,alnum=0;
double ans;
struct point
{
double x,y,v;
}a[1000005];
bool cmp(point a,point b)
{
return a.v<b.v;
}
int father(int p)
{
if(f[p]==p) return p;
return father(f[p]);
}
bool panduan(int a,int b)
{
if(father(a)==father(b)) return true;
else return false;
}
{
if(father(a)==father(b)) return true;
else return false;
}
void mixds(int a,int b)
{
int t1,t2;
t1=father(a);
t2=father(b);
f[t1]=t2;
}
int main()
{
cin>>s>>p;
for(i=1;i<=p;i++)
{
cin>>xx[i]>>yy[i];
for(j=1;j<=i-1;j++)
{
alnum++;
a[alnum].v=sqrt((xx[i]-xx[j])*(xx[i]-xx[j])+(yy[i]-yy[j])*(yy[i]-yy[j]));
a[alnum].x=i;
a[alnum].y=j;
}
{
int t1,t2;
t1=father(a);
t2=father(b);
f[t1]=t2;
}
int main()
{
cin>>s>>p;
for(i=1;i<=p;i++)
{
cin>>xx[i]>>yy[i];
for(j=1;j<=i-1;j++)
{
alnum++;
a[alnum].v=sqrt((xx[i]-xx[j])*(xx[i]-xx[j])+(yy[i]-yy[j])*(yy[i]-yy[j]));
a[alnum].x=i;
a[alnum].y=j;
}
}
for(i=1;i<=p;i++)
f[i]=i;
sort(a+1,a+alnum+1,cmp);
for(i=1;i<=alnum;i++)
{
if(panduan(a[i].x,a[i].y)) continue;
mixds(a[i].x,a[i].y);
ans=a[i].v;
total++;
if(total>=p-s) break;
}
printf("%.2lf",ans); //还是这个简单一点。
return 0;
}
for(i=1;i<=p;i++)
f[i]=i;
sort(a+1,a+alnum+1,cmp);
for(i=1;i<=alnum;i++)
{
if(panduan(a[i].x,a[i].y)) continue;
mixds(a[i].x,a[i].y);
ans=a[i].v;
total++;
if(total>=p-s) break;
}
printf("%.2lf",ans); //还是这个简单一点。
return 0;
}