#include<bits/stdc++.h>
#define N 1010
#define sqr(a) ((a)*(a))
#define fsb(a,b,c) for(register int a=b;a<=(c);a++)
#define fbs(a,b,c) for(register int a=b;a>=(c);a--)
using namespace std;
struct node{
 int x,y;
}a[N],b[N*N];
int n,m,cnt=0,fa[N];
inline double getdis(int i,int j){
 return sqrt(sqr(a[i].x-a[j].x)+sqr(a[i].y-a[j].y));
}
inline int cmp(node a,node b){
 return getdis(a.x,a.y)<getdis(b.x,b.y);
}
inline int getf(int x){
 return x==fa[x]?x:fa[x]=getf(fa[x]);
}
template<typename qw>inline void rll(qw &x){
 x=0;qw f=1;char c=getchar();
 while(!isdigit(c))f=c=='-'?-1:f,c=getchar();
 while(isdigit(c))x=x*10+c-'0',c=getchar();
}
int main(){
 rll(n);rll(m);
 fsb(i,1,n){
  rll(a[i].x);rll(a[i].y);
  fsb(j,1,i-1)b[++cnt]=(node){j,i};
 }
 sort(b+1,b+1+cnt,cmp);
 fsb(i,1,n)fa[i]=i;
 fsb(i,1,cnt){
  int fax=getf(b[i].x),fay=getf(b[i].y);
  if(fax==fay)continue;
  if(n==m){
   printf("%0.2lf",getdis(b[i].x,b[i].y));
   return 0;
  }
  fa[fay]=fax;
  n--;
 }
 return 0;
}