#include <stdio.h>
#include <atcoder/all>
#include <bits/stdc++.h>
using namespace std;
using namespace atcoder;
using mint = modint998244353;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf32 1000000001
#define Inf64 1000000000000000000LL


int main(){
	
	int N,K;
	cin>>N>>K;
	vector<double> x(N),y(N);
	rep(i,N) cin>>x[i]>>y[i];
	x.insert(x.begin(),0);
	y.insert(y.begin(),0);
	N++;
	vector dp(1<<N,vector(N,vector<double>(K+1,1e100)));
	dp[1][0][0] = 0.0;
	rep(i,1<<N){
		for(int k=K;k>=0;k--){
		rep(j,N){
			
				if(dp[i][j][k]==1e100)continue;
				rep(l,N){
					if(k==K&&l!=0)continue;
					if(l!=0&&((i>>l)&1))continue;
					double d = sqrt((x[j]-x[l])*(x[j]-x[l])+(y[j]-y[l])*(y[j]-y[l]));
					int ni = i|(1<<l);
					int nj = l;
					int nk = k+1;
					if(l==0)nk = 0;
					dp[ni][nj][nk] = min(dp[ni][nj][nk],dp[i][j][k]+d);
				}
			}
		}
	}
	cout<<fixed<<setprecision(20)<<dp[(1<<N)-1][0][0]<<endl;
	return 0;
}