#include<iostream>
#include<cstdio>
#include<cmath>
#include<iomanip>
#include<cstring>
using namespace std;
double w[101][101];
double dis[101];
double zuobiao[101][3];
bool pd[101]={0};
int team[1001];//spfa;
int main()
{
	freopen("short.in","r",stdin);
    freopen("short.out","w",stdout);
	int n,x,y,m,s,t,tail,head;
	int maxxx=99999999;
	cin>>n;
	for(int i=1;i<=n;i++)
	{
		dis[i]=maxxx;
		cin>>zuobiao[i][1]>>zuobiao[i][2];
	}
	for(int fz1=1;fz1<=n;fz1++)
	{
		for(int fz2=1;fz2<=n;fz2++)
			w[fz1][fz2]=maxxx;
	}
	cin>>m;
	for(int i=1;i<=m;i++)
	{
		cin>>x>>y;
		w[x][y]=w[y][x]=sqrt(pow(double(zuobiao[x][1]-zuobiao[y][1]),2)+pow(double(zuobiao[x][2]-zuobiao[y][2]),2));
	}
	cin>>s>>t;
	dis[s]=0;
	tail=1;
	pd[s]=true;
	head=0;
	team[1]=s;
	do
	{
		head++;
		int u=team[head];
		pd[u]=false;
		for(int ls=1;ls<=n;ls++)
		{
			if(w[u][ls]<maxxx)
			{
				if(dis[ls]>dis[u]+w[u][ls])
				{
					dis[ls]=dis[u]+w[u][ls];
					if(!pd[ls])
					{
						tail++;
						team[tail]=ls;
						pd[ls]=true;
					}
				}
			}
		}
	}
	while(head<tail);
	cout<<setiosflags(ios::fixed)<<setprecision(2);
	cout<<dis[t]<<endl;
	return 0;
}