#include<bits/stdc++.h>
#define MAXN 10000001
using namespace std;
struct node{
	int x,y;
	double dis;
}edge[MAXN],a[MAXN];
int n,k,m,fa[MAXN];
inline int get(const int &x){
	if(fa[x]==x){
		return x;
	}
	return fa[x]=get(fa[x]);
}
inline void merge(const int &x,const int &y){
	fa[get(x)]=get(y);
}
inline void kruskal(){
	for(int i=1;i<=m;++i){
		if(get(edge[i].x)!=get(edge[i].y)){
			--n;
			merge(edge[i].x,edge[i].y);
			if(n<=0){
				printf("%.2lf",edge[i].dis);
				return;
			}
		}
	}
}
inline bool cmp(const node &x,const node &y){
	return x.dis<y.dis;
}
inline double dist(const int &x,const int &y){
	return sqrt((a[x].x-a[y].x)*(a[x].x-a[y].x)+(a[x].y-a[y].y)*(a[x].y-a[y].y));
}
int main(){
	scanf("%d %d",&n,&k);
	for(int i=1;i<=n;++i){
		fa[i]=i;
	}	
	for(int i=1;i<=n;++i){
		scanf("%d %d",&a[i].x,&a[i].y);
	}
	for(int i=1;i<n;++i){
		for(int j=1;j<i;++j){
			edge[++m].x=i;
			edge[m].y=j;
			edge[m].dis=dist(i,j);
		}
	}
	sort(edge+1,edge+1+m,cmp);
	n-=k; 
	kruskal();
	return 0;
}