#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath>
#include<queue>
#define pdi pair<double,int>
using namespace std;
const int N=2010;
const int INF=0x3f3f3f3f;
int n,m;
int tot=0,ans=INF<<1;
struct place{
	int head,before;
	double xx,yy,dis;
}pl[N];
struct E{
	int nxt,to,vl;
}e[N];
inline void add_edge(int u,int v,double w)
{
	e[++tot].to=v;
	e[tot].vl=w;
	e[tot].nxt=pl[u].head;
	pl[u].head=tot;
}
inline double dist(double x1,double y1,double x2,double y2)
{
	return (double)sqrt((double)(x1-x2)*(x1-x2)+(double)(y1-y2)*(y1-y2));
}
inline void dij(int u,int v)
{
    for(int i=1;i<=n;i++) pl[i].dis=INF;
	pl[1].dis=0;
	priority_queue< pdi,vector<pdi>,greater<pdi> >q;
	q.push({0,1});
	while(!q.empty())
	{
		pdi tmp=q.top();
		q.pop();
		double d=tmp.first;
		int x=tmp.second;
		if(pl[x].dis!=d) continue;
		for(int i=pl[x].head;i;i=e[i].nxt)
		{
			int y=e[i].to;
			if((u==x&&v==y)||(u==y)&&(v==x)) continue;
			if(pl[y].dis<pl[x].dis+e[i].vl) continue;
			if(u==-1&&v==-1) pl[v].before=u;
			pl[y].dis=pl[x].dis+e[i].vl;
			q.push({pl[y].dis,y});
		}
	}
}
int main()
{
	cin>>n>>m;
	for(int i=1;i<=n;i++) cin>>pl[i].xx>>pl[i].yy;
	for(int i=1;i<=m;i++)
	{   
	    int u,v; 
		cin>>u>>v;
		double w=dist(pl[u].xx,pl[u].yy,pl[v].xx,pl[v].yy);
		add_edge(u,v,w);
		add_edge(v,u,w);
	}
	dij(-1,-1);
	for(int i=n;i!=1;i=pl[i].before)
	{
		dij(i,pl[i].before);
		ans=min(ans,pl[n].before);
	}
	if(ans>=INF) cout<<"-1"<<endl;
	else printf("%.2lf\n",ans);
	return 0; 
} 
/*
3 3
0 0
1 1
0 2
1 2
1 3
2 3

2.83
*/