#include <bits/stdc++.h>
using namespace std;

#define rep(i,m,n) for(int (i)=(int)(m);i<(int)(n);++i)
#define rep2(i,m,n) for(int (i)=(int)(n)-1;i>=(int)(m);--i)
#define REP(i,n) rep(i,0,n)
#define REP2(i,n) rep2(i,0,n)
#define FOR(i,c) for(decltype((c).begin())i=(c).begin();i!=(c).end();++i)
#define all(hoge) (hoge).begin(),(hoge).end()
#define en '\n'
using ll = long long;
using ull = unsigned long long;
template <class T> using vec = vector<T>;
template <class T> using vvec = vector<vec<T>>;
typedef pair<ll, ll> P;
constexpr long long INF = 1LL << 60;
constexpr int INF_INT = 1 << 25;
//constexpr long long MOD = (ll) 1e9 + 7;
constexpr long long MOD = 998244353LL;
using ld=long double;
static const ld pi = 3.141592653589793L;
typedef vector<ll> Array;
typedef vector<Array> Matrix;


template<class T> inline bool chmin(T& a, T b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template<class T> inline bool chmax(T& a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}

struct Edge {
	ll to, rev;
    long double cap;
	Edge(ll _to, long double _cap, ll _rev) {
	to = _to; cap = _cap; rev = _rev;
	}
};
using Edges = vector<Edge>;
using Graph = vector<Edges>;

void add_edge(Graph& G, ll from, ll to, long double cap, bool revFlag, long double revCap) {
	G[from].push_back(Edge(to, cap, (ll)G[to].size()));
	if (revFlag)G[to].push_back(Edge(from, revCap, (ll)G[from].size() - 1));
}

using P2 = pair<long double, ll>;

void Dijkstra(Graph& G, ll s, vec<long double>& d) {//O(|E|log|V|)
  d.resize(G.size());
  REP(i, d.size())d[i] = INF;
  d[s] = 0;
  priority_queue<P2, vector<P2>, greater<P2>> q;
  q.push(make_pair(0.0L, s));
  while (!q.empty()) {
    P a = q.top();
    q.pop();
    if (d[a.second] < a.first)continue;
    REP(i, G[a.second].size()) {
      Edge e = G[a.second][i];
      if (d[e.to] > d[a.second] + e.cap) {
        d[e.to] = d[a.second] + e.cap;
        q.push(make_pair(d[e.to], e.to));
      }
    }
  }
}



void solve(){
    ll n,m,x,y;
    cin>>n>>m>>x>>y;
    x--;y--;
    vec<long double> p(n),q(n);
    REP(i,n) cin>>p[i]>>q[i];

    auto dis = [&](int i, int j){
        return sqrt((p[i]-p[j])*(p[i]-p[j])+(q[i]-q[j])*(q[i]-q[j]));
    };
    Graph g(n);
    REP(i,m){
        ll a,b;
        cin>>a>>b;
        a--;b--;
        add_edge(g,a,b,dis(a,b),true,dis(a,b));
    }
    vec<long double> d;
    Dijkstra(g,x,d);
    cout<<fixed<<setprecision(10)<<d[y]<<en;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
	
	solve();
	//ll t;cin>>t;REP(i,t) solve();

    return 0;
}