#include <bits/stdc++.h>
using namespace std;
const int N=16;
int n,cnt;
double x[N],y[N],dist[N][N];
double ans;
bool vis[N];
void dfs(int deep,int now,double sum){
	cnt++;
	if(cnt>=10000000){
		printf("%.2lf",ans);
		exit(0);
	}
	if(deep>n){
		if(sum<ans) ans=sum;
		return ;
	}
	for(int i=1;i<=n;i++){
		if(!vis[i]){
			double t=sum+dist[now][i];
			if(t>=ans) continue;
			vis[i]=1;
			dfs(deep+1,i,t);
			vis[i]=0;
		}
	}
}
int main(){

	ios::sync_with_stdio(false);
	cin.tie(0);cout.tie(0);
	cin>>n;
	ans=1e6;
	x[0]=y[0]=0;
	for(int i=1;i<=n;i++) cin>>x[i]>>y[i];
	for(int i=0;i<=n;i++) for(int j=0;j<=n;j++) dist[i][j]=sqrt((x[i]-x[j])*(x[i]-x[j])+(y[i]-y[j])*(y[i]-y[j]));
	dfs(1,0,0);
	printf("%.2lf",ans);

	return 0;
}

测试结果