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

#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")

#define int long long

using ld=long double;

signed main(){
	int N,K;cin>>N>>K;
	vector<int> X(N+1),Y(N+1);
	for(int i=0;i<N;i++){
		cin>>X[i]>>Y[i];
	}

	vector<vector<ld>> d(N+1,vector<ld>(N+1));

	for(int i=0;i<=N;i++){
		for(int j=0;j<=N;j++){
			d[i][j]=hypotl(X[i]-X[j],Y[i]-Y[j]);
		}
	}

	X[N]=0,Y[N]=0;

	vector<ld> cost(1<<N);

	// cout<<"!"<<endl;

	for(int S=1;S<(1<<N);S++){
		vector<int> v={N};
		for(int i=0;i<N;i++){
			if(S>>i&1)v.push_back(i);
		}

		int n=v.size();

		vector<vector<ld>> dp(1<<n,vector<ld>(n,1e18));

		dp[0][0]=0;

		for(int s=0;s<(1<<n);s++){
			for(int j=0;j<n;j++){
				for(int k=0;k<n;k++){
					if(s>>k&1)continue;

					dp[s|(1<<k)][k]=min(dp[s|(1<<k)][k],dp[s][j]+d[v[j]][v[k]]);					
				}
			}
		}

		cost[S]=dp[(1<<n)-1][0];

		// cout<<S<<" : "<<dp[(1<<n)-1][0]<<endl;
	}

	
	// cout<<"!"<<endl;

	vector<ld> dp(1<<N,1e18);

	dp[0]=0;

	for(int S=0;S<(1<<N);S++){
		int al=(1<<N)-1;

		int st=al^S;
		int sub=st;

		while(sub){
			if(__popcount(sub)<=K){
				dp[S|sub]=min(dp[S|sub],dp[S]+cost[sub]);
			}
			sub=(sub-1)&st;
		}
	}

	cout<<fixed<<setprecision(20)<<dp[(1<<N)-1]<<endl;
}