#pragma GCC optimize("O3", "unroll-loops")

#include <bits/stdc++.h>

using namespace std;

#define ll long long
#define ld long double

template<typename T>
vector<T> dijkstra(int s, vector<vector<pair<int, T>>> &G){
    const int n = G.size();
    vector<T> d(n, numeric_limits<T>::max());
    vector<int> b(n, -1);
    priority_queue<pair<T, int>, vector<pair<T, int>>, greater<pair<T, int>>> q;
    d[s] = 0;
    q.emplace(d[s], s);
    while (!q.empty()){
        pair<T, int> p = q.top();
        q.pop();
        int v = p.second;
        if (d[v] < p.first) continue;
        for (auto& e : G[v]){
            int u = e.first;
            T c = e.second;
            if (d[u] > d[v] + c){
                d[u] = d[v] + c;
                b[u] = v;
                q.emplace(d[u], u);
            }
        }
    }
    return d;
}

int N, M;
int X, Y;
vector<pair<int, int>> pq;

void input(void){
    cin >> N >> M;
    pq.resize(N);
    cin >> X >> Y;
    --X, --Y;
    for (int i = 0; i < N; ++i)
        cin >> pq[i].first >> pq[i].second;
}

ld dist(int a, int b){
    int dx = pq[a].first - pq[b].first;
    int dy = pq[a].second - pq[b].second;
    return sqrtl(dx * dx + dy * dy);
}

int main(void){
    input();
    vector<vector<pair<int, ld>>> g(N);
    for (int i = 0; i < M; ++i){
        int P, Q; cin >> P >> Q;
        --P, --Q;
        ld cost = dist(P, Q);
        g[P].emplace_back(Q, cost);
        g[Q].emplace_back(P, cost);
    }
    auto d = dijkstra(X, g);
    cout << setprecision(15) << d[Y] << endl;
    return 0;
}