#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;

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<vector<long double>>> dp(1 << N, vector<vector<long double>>(N + 1, vector<long double>(K + 1, INF)));
	dp[0][N][K] = 0;
	rep(bit, 1 << N){
		rep(from, N + 1){
			if(from < N) if((~bit >> from) & 1) continue;
			for(int k = 1; k <= K; k++){
				rep(to, N){
					if((bit >> to) & 1) continue;
					chmin(dp[bit | (1 << to)][to][k - 1], dp[bit][from][k] + dist[from][to]);
				}
			}
			for(int k = 0; k <= K; k++) chmin(dp[bit][N][K], dp[bit][from][k] + dist[from][N]);
		}
	}
	cout << setprecision(15);
	cout << dp[(1 << N) - 1][N][K] << "\n";
	return 0;
}