#include<bits/stdc++.h>
#define REP(i,n) for(int i=0,i##_len=int(n);i<i##_len;++i)
#define rep(i,a,b) for(int i=int(a);i<int(b);++i)
#define All(x) (x).begin(),(x).end()
#define rAll(x) (x).rbegin(),(x).rend()
using namespace std;
using ll = long long;

int main(){
    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];
    using P = pair<double,int> ;
    vector<vector<P>> graph(N);
    REP(i,M){
        int a,b; cin>>a>>b;
        a--;b--;
        double c = sqrt(pow(p[a]-p[b],2) + pow(q[a]-q[b],2));
        graph[a].push_back(P(c,b));
        graph[b].push_back(P(c,a));
    }
    vector<double> dist(N,1e9);
    priority_queue<P,vector<P>,greater<>> que;
    dist[X]=0;
    que.push(P(0,X));
    while(!que.empty()){
        P p=que.top();que.pop();
        int u=p.second;
        if(dist[u]<p.first) continue;
        REP(j,graph[u].size()){
            int v=graph[u][j].second;
            double alt=dist[u]+graph[u][j].first;
            if(dist[v]>alt){
                dist[v]=alt;
                que.push(P(alt,v));
            }
        }
    }
    printf("%.16f\n",dist[Y]);
}