#include <bits/stdc++.h>
using namespace std;
#define MOD (long long int)(1e9+7)
#define ll long long int
#define rep(i,n) for(int i=0; i<(int)(n); i++)
#define reps(i,n) for(int i=1; i<=(int)(n); i++)
#define REP(i,n) for(int i=n-1; i>=0; i--)
#define REPS(i,n) for(int i=n; i>0; i--)
#define FOR(i,a,b) for(int i=a; i<(int)(b); i++)
#define ALL(x) (x).begin(),(x).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define CLR(a) memset((a), 0 ,sizeof(a))
#define PB push_back
#define MP make_pair
#define SP << " " <<
const int INF = 1001001001;
const ll LINF = 100100100100100100;
const double EPS = 1e-10;
const long double PI  = acos(-1.0L);
typedef pair<int,int> PII;
typedef pair<ll,ll> PLL;
typedef pair<double,double> PDD;
typedef pair<double,int> PDI;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<ll> VL;
#define chmax(a,b) a = (((a)<(b))?(b):(a))
#define chmin(a,b) a = (((a)>(b))?(b):(a))

__attribute__((constructor))
void initial(){
	cin.tie(nullptr);
	ios::sync_with_stdio(false);
	cout << fixed << setprecision(15);
}

// queueを用いた場合の実装(経路復元無し)
const int MAX_E = 200100;
const int MAX_V = 200100;
struct edge{int to; double cost;};
int V;
vector<edge> G[MAX_V];
double d[MAX_V];

void dijkstra(int s){
  // greater<PII>を指定することでfirstが小さい順に取り出せるようにする
  priority_queue<PDI, vector<PDI>, greater<PDI> > que;
  fill(d,d+V,(double)INF); d[s] = 0.0; que.push(MP(0.0,s));
  while(!que.empty()){
    PII p = que.top(); que.pop();
    int v = p.second;
    if(d[v]<p.first) continue;
    rep(i,G[v].size()){
      edge e = G[v][i];
      if(d[e.to]>d[v]+e.cost){
        d[e.to] = d[v]+e.cost;
        que.push(PII(d[e.to], e.to));
      }
    }
  }
}




signed main(){
	int n,m; cin>>n>>m; V=n;
	int x,y; cin>>x>>y; x--; y--;
	vector<PDD> t;
	rep(i,n){
		double p,q; cin>>p>>q;
		t.PB(MP(p,q));
	}
	rep(i,m){
		int p,q; cin>>p>>q; p--; q--;
		double d=pow(pow(t[p].first-t[q].first,2.0)+pow(t[p].second-t[q].second,2.0),0.50);
		edge e1; e1.to=q; e1.cost=d; G[p].PB(e1);
		e1.to=p; G[q].PB(e1);
	}
	dijkstra(x);
	cout<<d[y]<<endl;


	return 0;
}