AC

#include<bits/stdc++.h>
using namespace std;
struct shop{
	int x,y;
}d[105]; 
struct road{
	int l,r;		//起点编号，终点编号 
	double k;		//路径距离 
}el[1005];
double exc(shop a,shop b){
	return sqrt(pow(a.x-b.x,2)+pow(a.y-b.y,2));
}
double dis[105];		//距s距离 
int main(){
	int n,m,s,t;
	cin>>n;
	for(int i=1;i<=n;i++){
		cin>>d[i].x>>d[i].y;
	}
	cin>>m;
	for(int i=0;i<m;i++){
		cin>>el[i].l>>el[i].r;
		el[i].k=exc(d[el[i].l],d[el[i].r]);
	}
	cin>>s>>t;
	for(int i=1;i<=n;i++) dis[i]=114514.0;		//初始化 
	dis[s]=0.0;		//到自己距离为0 
	for(int i=0;i<n-1;i++){
		for(int j=0;j<m;j++){
			dis[el[j].r]=min(dis[el[j].r],dis[el[j].l]+el[j].k);
			dis[el[j].l]=min(dis[el[j].l],dis[el[j].r]+el[j].k);
		}
	}
	printf("%.2f",dis[t]);
	return 0;
}