#include<bits/stdc++.h>
#define rep(i,n) for(int i=0;i<n;i++)
using namespace std;
template<typename T> void chmin(T& a, T b){a = min(a, b);}

const long double INF = 8000000000000000;

template<typename T> ostream& operator<<(ostream& os, const vector<T>& v){int n = v.size(); rep(i, n) os << v[i] << (i == n - 1 ? "\n" : " "); return os;}
template<typename T> ostream& operator<<(ostream& os, const vector<vector<T>>& v){int n = v.size(); rep(i, n) os << v[i] << (i == n - 1 ? "\n" : ""); return os;}

int main(){
	int N, K;
	cin >> N >> K;
	vector<long long> x(N + 1), y(N + 1);
	rep(i, N) cin >> x[i] >> y[i];
	x[N] = 0; y[N] = 0;
	vector<vector<long double>> dist(N + 1, vector<long double>(N + 1));
	rep(i, N + 1) rep(j, N + 1){
		long double res = (x[i] - x[j]) * (x[i] - x[j]) + (y[i] - y[j]) * (y[i] - y[j]);
		dist[i][j] = sqrtl(res);
	}
	vector<vector<long double>> f(1 << N, vector<long double>(N + 1, INF));
	f[0][N] = 0;
	rep(bit, 1 << N){
		rep(from, N + 1){
		if(from < N) if((~bit >> from) & 1) continue;
			rep(to, N){
				if((bit >> to) & 1) continue;
				chmin(f[bit | (1 << to)][to], f[bit][from] + dist[from][to]);
			}
		}
	}
	vector<long double> g(1 << N, INF);
	rep(bit, 1 << N){
		int cnt = __builtin_popcount(bit);
		if(cnt <= K){
			rep(from, N){
				chmin(g[bit], f[bit][from] + dist[from][N]);
			}
		}
	}
	rep(bit1, 1 << N){
		for(int bit2 = bit1; bit2 > 0; bit2 = ((bit2 - 1) & bit1)){
			chmin(g[bit1], g[bit1 - bit2] + g[bit2]);
		}
	}
	cout << setprecision(15);
	cout << g[(1 << N) - 1] << "\n";
	return 0;
}