/**
	author:  shobonvip
	created: 2024.11.10 22:38:49
**/

#include<bits/stdc++.h>
using namespace std;

//* ATCODER
#include<atcoder/all>
using namespace atcoder;
typedef modint998244353 mint;
//*/

/* BOOST MULTIPRECISION
#include<boost/multiprecision/cpp_int.hpp>
using namespace boost::multiprecision;
//*/

typedef long long ll;

#define rep(i, s, n) for (int i = (int)(s); i < (int)(n); i++)
#define rrep(i, s, n) for (int i = (int)(n)-1; i >= (int)(s); i--)

template <typename T> bool chmin(T &a, const T &b) {
	if (a <= b) return false;
	a = b;
	return true;
}

template <typename T> bool chmax(T &a, const T &b) {
	if (a >= b) return false;
	a = b;
	return true;
}

template <typename T> T max(vector<T> &a){
	assert(!a.empty());
	T ret = a[0];
	for (int i=0; i<(int)a.size(); i++) chmax(ret, a[i]);
	return ret;
}

template <typename T> T min(vector<T> &a){
	assert(!a.empty());
	T ret = a[0];
	for (int i=0; i<(int)a.size(); i++) chmin(ret, a[i]);
	return ret;
}

template <typename T> T sum(vector<T> &a){
	T ret = 0;
	for (int i=0; i<(int)a.size(); i++) ret += a[i];
	return ret;
}

int main(){
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	
	int n, k; cin >> n >> k;
	vector<double> x(n+1), y(n+1);
	rep(i,0,n) cin >> x[i] >> y[i];
	

	vector d(1<<n, vector(n+1, vector<double>(k+1, 1e18)));
	priority_queue<tuple<double,int,int,int>> pq;
	d[0][n][k] = 0;
	pq.push(tuple(0, 0, n, k));

	double eps = 1e-9;

	auto dist = [&](int i, int j) -> double {
		return sqrt((x[i]-x[j])*(x[i]-x[j]) + (y[i]-y[j])*(y[i]-y[j]));
	};

	while(!pq.empty()){
		auto [tmp, s, i, v] = pq.top();
		pq.pop();
		tmp = -tmp;
		if (d[s][i][v] + eps < tmp) continue;
		
		rep(j,0,n+1) {
			int t = (j == n ? s : s | (1 << j));
			int w = (j == n ? k : v - 1);
			if (w >= 0 && chmin(d[t][j][w], dist(i, j) + tmp)) {
				pq.push(tuple(-d[t][j][w], t, j, w));
			}
		}
	}

	cout << setprecision(15);
	cout << d[(1<<n)-1][n][k] << '\n';
}