#include <bits/stdc++.h>
using namespace std;
using ll = long long;
template <class T, class U> using Pa = pair<T, U>;
template <class T> using vec = vector<T>;
template <class T> using vvec = vector<vec<T>>;


int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    int N,M;
    cin >> N >> M;
    int S,T;
    cin >> S >> T;
    S--; T--;
    vec<int> P(N),Q(N);
    for(int i=0;i<N;i++) cin >> P[i] >> Q[i];
    
    auto dist = [&](int i,int j){
        double dx = P[i]-P[j],dy = Q[i]-Q[j];
        return sqrt(dx*dx+dy*dy);
    };
    
    vvec<Pa<double,int>> g(N);
    for(int i=0;i<M;i++){
        int a,b;
        cin >> a >> b;
        a--; b--;
        double d = dist(a,b);
        g[a].push_back({d,b});
        g[b].push_back({d,a});
    }
    double inf = 1e9;
    vec<double> D(N,inf);
    vec<int> check(N,0);
    priority_queue<Pa<double,int>,vec<Pa<double,int>>,greater<Pa<double,int>>> que;
    que.push({0.0,S});
    D[S] = 0;
    while(!que.empty()){
        auto [d,cur] = que.top(); que.pop();
        if(check[cur]) continue;
        check[cur] = 1;
        for(auto& e:g[cur]){
            double nd = d+e.first;
            if(D[e.second]>nd){
                D[e.second] = nd;
                que.push({nd,e.second});
            }
        }
    }
    cout << fixed << setprecision(10) << D[T] << "\n";
}