#include <bits/stdc++.h>

using namespace std;

#define DBG cerr << '!' << endl;
#define REP(i,n) for(ll (i) = (0);(i) < (n);++i)
#define rep(i,s,g) for(ll (i) = (s);(i) < (g);++i)
#define rrep(i,s,g) for(ll (i) = (s);i >= (g);--(i))
#define PB push_back
#define MP make_pair
#define FI first
#define SE second
#define SHOW1d(v,n) {for(int W = 0;W < (n);W++)cerr << v[W] << ' ';cerr << endl << endl;}
#define SHOW2d(v,i,j) {for(int aaa = 0;aaa < i;aaa++){for(int bbb = 0;bbb < j;bbb++)cerr << v[aaa][bbb] << ' ';cerr << endl;}cerr << endl;}
#define ALL(v) v.begin(),v.end()
#define Decimal fixed<<setprecision(10)
#define INF 1000000000
#define MOD 1000000007

typedef long long ll;
typedef pair<ll,ll> P;

const double PI=acos(-1);
const double EPS=1e-4;

int N,M;
double x[22],y[22];

bool check(double mid){
	vector<int> m_list;
	
	REP(i,N){
		m_list.PB(1<<i);
	}
	
	REP(i,N)REP(j,N){
		if(i==j)continue;
		double dx=x[i]-x[j],dy=y[i]-y[j];
		double d=sqrt(dx*dx+dy*dy);
		if(d>mid*2+EPS)continue;
		double r=sqrt(mid*mid-d*d/4);
		double vx=-dy/d*r;
		double vy=dx/d*r;

		double xx=(x[i]+x[j])/2+vx;
		double yy=(y[i]+y[j])/2+vy;
		int cnt=0;
		REP(k,N){
			if((x[k]-xx)*(x[k]-xx)+(y[k]-yy)*(y[k]-yy)<mid*mid+EPS)cnt |= (1<<k);
		}
		m_list.PB(cnt);
	}

	/*
	REP(i,m_list.size()){
		cout << (static_cast<bitset<(unsigned)(10)>>(m_list[i])) << endl;
	}
*/	
	
	vector<int> dp(1 << N,INF);
	dp[0] = 0;
	REP(i,dp.size()){
		REP(j,m_list.size()){
			dp[i | m_list[j]] = min(dp[i] + 1 , dp[i | m_list[j]]);
		}
	}
	
	if(dp[(1 << N )- 1] == INF){
		REP(i,dp.size()){
			cout << (static_cast<bitset<(unsigned)(10)>>(dp[i])) << ' ' << dp[i] << endl;
		}
	}
	
	//cout << dp[(1 << N)-1] << endl;
	return (dp[(1 << N)-1] <= M);
}

int main()
{
	cin >> N >> M;
	vector<pair<int,int>> v;
	REP(i,N){
		int a,b;cin >> a >> b;
		v.PB(MP(a,b));
	}
	
	sort(ALL(v));
	
	v.erase(unique(ALL(v)),v.end());
	
	REP(i,v.size()){
		x[i] = v[i].FI;
		y[i] = v[i].SE;
	}
	
	N = v.size();
	
	double top = 1000000;
	double under = 0;
		
	REP(i,100){
		double mid = (top + under) / 2;
	//	cout << mid << endl;
		if(check(mid))top = mid;
		else under = mid;
	}
	
	cout << Decimal << top << endl;	

	
	return 0;
}
