#include<cstdio>

#include<iostream>

#include<cstring>

#include<algorithm>

#include<cmath>

#define ull unsigned long long

#define ll long long

#define R register int

using namespace std;

#define pause (for(R i=1;i<=10000000000;++i))

#define In freopen("NOIPAK++.in","r",stdin)

#define Out freopen("out.out","w",stdout)

namespace Fread {

static char B[<<],*S=B,*D=B;

#ifndef JACK

#define getchar() (S==D&&(D=(S=B)+fread(B,1,1<<15,stdin),S==D)?EOF:*S++)

#endif

inline int g() {

    R ret=,fix=; register char ch; while(!isdigit(ch=getchar())) fix=ch=='-'?-:fix;

    if(ch==EOF) return EOF; do ret=ret*+(ch^); while(isdigit(ch=getchar())); return ret*fix;

} inline bool isempty(const char& ch) {return (ch<=||ch>=);}

inline void gs(char* s) {

    register char ch; while(isempty(ch=getchar()));

    do *s++=ch; while(!isempty(ch=getchar()));

}

} using Fread::g; using Fread::gs;

namespace Luitaryi {

const int N=,M=N*N;

int n,k,cnt,tot,fa[N];

double ans;

struct node {int x,y;}p[N];

#define x(i) p[i].x

#define y(i) p[i].y

struct edge { int u,v; double w; edge() {}

    edge(int uu,int vv,double ww) {u=uu,v=vv,w=ww;}

    inline bool operator <(const edge& that) {return w<that.w;}

}e[M];

inline int getf(int x) {return x==fa[x]?x:fa[x]=getf(fa[x]);}

inline void main() {

    n=g(),k=g();

    for(R i=;i<=n;++i) x(i)=g(),y(i)=g();

    for(R i=;i<=n;++i) for(R j=i+;j<=n;++j)

        e[++cnt]=edge(i,j,sqrt((x(i)-x(j))*(x(i)-x(j))+(y(i)-y(j))*(y(i)-y(j))));

    sort(e+,e+cnt+); for(R i=;i<=n;++i) fa[i]=i;

    for(R i=;i<=cnt;++i) { R u=e[i].u,v=e[i].v; register double w=e[i].w;

        R uf=getf(u),vf=getf(v);

        if(uf==vf) continue;

        else {

            ans=w; ++tot;

            fa[uf]=vf;

            if(tot==n-k+) break;

        }

    } printf("%.2lf",ans);

}

}

signed main() {

    Luitaryi::main();

}