#include <bits/stdc++.h>

using namespace std;

using ll = long double;

constexpr char newl = '\n';

struct State {
    int at;
    ll cost;
    //int prev;
    State(int at, ll cost/*, int prev*/) : at(at), cost(cost)/*, prev(prev)*/ {}
    bool operator>(const State& s) const {
        return cost > s.cost;
    }
};

struct Edge {
    int to;
    ll cost;
    Edge(int to, ll cost) : to(to), cost(cost) {}
};

using Graph = vector< vector<Edge> >; //隣接リスト

const ll INF = 1e15;
//const int NONE = -1;

//sは始点、mincは最短経路のコスト、prevsは最短経路をたどる際の前の頂点
void dijkstra(int s, const Graph& graph, vector<ll>& minc/*, vector<int>& prevs*/){
    minc.assign(graph.size(), INF);
    //prevs.assign(graph.size(), NONE);

    priority_queue<State, vector<State>, greater<State> > pq;
    pq.emplace(s, 0/*, NONE*/);
    minc[s] = 0;

    while(!pq.empty()) {
        State cur = pq.top();
        pq.pop();
        if (minc[cur.at] < cur.cost) continue;

        for(const Edge& e : graph[cur.at]) {
            ll cost = cur.cost + e.cost;
            if (minc[e.to] <= cost) continue;
            minc[e.to] = cost;
            //prevs[e.to] = cur.at;
            pq.emplace(e.to, cost/*, cur.at*/);
        }
    }
}

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    int n, m;
    cin >> n >> m;

    int x, y;
    cin >> x >> y;
    --x; --y;

    vector<double> p(n), q(n);
    for (int i = 0; i < n; i++) {
        cin >> p[i] >> q[i];
    }

    Graph g(n);

    for (int i = 0; i < m; i++) {
        int u, v;
        cin >> u >> v;
        --u; --v;

        ll cost = hypot(p[u] - p[v], q[u] - q[v]);
        g[u].emplace_back(v, cost);
        g[v].emplace_back(u, cost);
    }

    vector<ll> minc;
    dijkstra(x, g, minc);

    cout << fixed << setprecision(15) << minc[y] << newl;
    return 0;
}