#include<bits/stdc++.h>
using namespace std;
int n,m,x[514],y[514],vis[514];double dis[514],dis2[514];
vector<int>e[514];
vector<double>c[514];
struct s{
	int id;
	double w;
};
bool operator<(s x,s y){
	return x.w>y.w;
}
priority_queue<s>q;
void dijkstra(){
	dis[1]=0;
	q.push((s){1,0});
	while(!q.empty()){
		int u=q.top().id,now=q.top().w;q.pop();
		vis[u]=1;
		for(int i=0,len=e[u].size();i<len;i++){
			int v=e[u][i];double w=c[u][i];
			if(vis[v])continue;
			bool p=0;
			if(dis[v]>dis[u]+w)dis[v]=dis[u]+w,p=1;
			if(dis[v]<dis[u]+w&&dis2[v]>dis[u]+w)dis2[v]=dis[u]+w,p=1;
			if(dis2[v]>dis2[u]+w)dis2[v]=dis2[u]+w,p=1;
			if(p)q.push((s){v,dis[v]});
		}
	}
}
int main(){
	cin>>n>>m;
	for(int i=1;i<=n;i++)dis[i]=dis2[i]=1145141919;
	for(int i=1;i<=n;i++)scanf("%d%d",&x[i],&y[i]);
	for(int i=1,u,v;i<=m;i++){
		scanf("%d%d",&u,&v);
		e[u].push_back(v);
		e[v].push_back(u);
		c[u].push_back(sqrt(double(abs(x[u]-x[v])*abs(x[u]-x[v])+abs(y[u]-y[v])*abs(y[u]-y[v]))));
		c[v].push_back(sqrt(double(abs(x[u]-x[v])*abs(x[u]-x[v])+abs(y[u]-y[v])*abs(y[u]-y[v]))));
	}
	dijkstra();
	if(!vis[n])printf("-1");
	else printf("%0.2lf",dis2[n]);
}