#include<bits/stdc++.h>

#define rep(i,x,y) for(register int i=x;i<=y;i++)

#define dec(i,x,y) for(register int i=x;i>=y;i--)

#define eps 1e-4

using namespace std;

const int N=;

inline int read(){

    int x=,f=;char ch=getchar();

    while(!isdigit(ch)){if(ch=='-')f=-;ch=getchar();}

    while(isdigit(ch)){x=(x<<)+(x<<)+(ch^);ch=getchar();}

    return x*f;}

int n,k,x[N],y[N],mx,my,fa[N];

inline int find(int x){

    return fa[x]==x?x:fa[x]=find(fa[x]);}

inline int S(int x){return x*x;}

inline double dis(int i,int j){

return S(x[j]-x[i])+S(y[j]-y[i]);}

bool check(double mid){

    rep(i,,n) fa[i]=i;int cnt=;

    rep(i,,n)rep(j,,n)

       if(dis(i,j)<=mid){

       int xx=find(i),yy=find(j);

       if(xx!=yy) fa[xx]=yy;}

    rep(i,,n) if(find(i)==i) cnt++;

    if(cnt<k) return ;return ;}

int main(){

    double mx=0.0,my=0.0;

    n=read();k=read();

    rep(i,,n){

        x[i]=read();y[i]=read();

        mx=mx>x[i]?mx:x[i];

        my=my>y[i]?my:y[i];}

    double l=0.00,r=S(mx)+S(my),mid;

    while(r-l>eps){

        mid=(l+r)*0.5;

        if(check(mid)) l=mid;

        else r=mid;}

    printf("%.2lf\n",sqrt(l));return ;

}