#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<ll,ll> P;
typedef pair<int,int> Pi;
#define rep(i,n) for(ll i=0;i<n;i++)
#define FOR(i,a,b) for(ll i=a;i<b;i++)
#define fi first
#define se second
#define endl "\n"

template<typename T> inline bool chmax(T &a, T b){if(a<b){a=b;return true;}return false;}
template<typename T> inline bool chmin(T &a, T b){if(a>b){a=b;return true;}return false;}
template<typename T> ostream& operator<<(ostream& s,const complex<T>& d) {return s<<"("<<d.real()<<", "<<d.imag()<< ")";}
template<typename T1, typename T2> ostream& operator<<(ostream& s,const pair<T1,T2>& d) {return s<<"("<<d.first<<", "<<d.second<<")";}
template<typename T> ostream& operator<<(ostream& s, const vector<T>& d){int len=d.size();rep(i,len){s<<d[i];if(i<len-1) s<<" ";}return s;}
template<typename T> ostream& operator<<(ostream& s,const vector<vector<T>>& d){int len=d.size();rep(i,len){s<<d[i]<<endl;}return s;}
template<typename T> ostream& operator<<(ostream& s,const set<T>& v){s<<"{ ";for(auto itr=v.begin();itr!=v.end();++itr) {if (itr!=v.begin()) {s<< ", ";}s<<(*itr);}s<<" }";return s;}
template<typename T> ostream& operator<<(ostream& s,const multiset<T>& v){s<<"{ ";for(auto itr=v.begin();itr!=v.end();++itr) {if (itr!=v.begin()) {s<< ", ";}s<<(*itr);}s<<" }";return s;}
template<typename T1, typename T2> ostream& operator<<(ostream& s,const map<T1,T2>& m){s<<"{"<<endl;for(auto itr=m.begin();itr!=m.end();++itr){s<<" "<<(*itr).first<<" : "<<(*itr).second<<endl;}s<<"}"<<endl;return s;}

const ll mod=1e9+7;
const ll inf=1e17;
const int INF=1e9;
const double EPS=1e-10;
const double PI=acos(-1);

struct edge{
	int to;
	double cost;
};

int main(){
	cin.tie(0);ios::sync_with_stdio(false);
	int n,m;
	cin>>n>>m;
	int x,y;
	cin>>x>>y;
	x--,y--;
	vector<double> p(n),q(n);
	rep(i,n){
		cin>>p[i]>>q[i];
	}
	auto calc=[&](pair<double,double> a,pair<double,double> b){
		return sqrt((a.fi-b.fi)*(a.fi-b.fi)+(a.se-b.se)*(a.se-b.se));
	};
	vector<vector<edge>> g(n);
	rep(i,m){
		int u,v;
		cin>>u>>v;
		u--,v--;
		double d=calc(pair<double,double>(p[u],q[u]),pair<double,double>(p[v],q[v]));
		g[u].push_back({v,d});
		g[v].push_back({u,d});
	}
	auto dijkstra=[&](int st,int en){
		priority_queue<pair<double,int>,vector<pair<double,int>>,greater<pair<double,int>>> que;
		vector<double> dist(n,inf);
		vector<int> pre(n);
		dist[st]=0;
		que.push({0,st});
		while(!que.empty()){
			auto hoge=que.top();
			que.pop();
			int v=hoge.se;
			double d=hoge.fi;
			if(dist[v]<d) continue;
			for(auto e:g[v]){
				if(chmin(dist[e.to],dist[v]+e.cost)){
					que.push({dist[e.to],e.to});
					pre[e.to]=v;
				}
			}
		}
		return dist[en];
	};
	cout<<setprecision(20)<<dijkstra(x,y)<<endl;
}