#include <iostream>
#include <iomanip>
#include <cmath>
#include <vector>
#include <tuple>
#include <queue>
#include <limits>

template <class T>
using MinHeap = std::priority_queue<T, std::vector<T>, std::greater<T>>;

template <class Cost = int>
struct Edge {
    int src, dst;
    Cost cost;
    Edge(int src = -1, int dst = -1, Cost cost = 1)
        : src(src), dst(dst), cost(cost){};

    bool operator<(const Edge<Cost>& e) const { return this->cost < e.cost; }
    bool operator>(const Edge<Cost>& e) const { return this->cost > e.cost; }
};

template <class Cost = int>
struct Graph {
    std::vector<std::vector<Edge<Cost>>> graph;

    Graph(int n = 0) : graph(n) {}

    void span(bool direct, int src, int dst, Cost cost = 1) {
        graph[src].emplace_back(src, dst, cost);
        if (!direct) graph[dst].emplace_back(dst, src, cost);
    }

    int size() const { return graph.size(); }
    void clear() { graph.clear(); }
    void resize(int n) { graph.resize(n); }

    std::vector<Edge<Cost>>& operator[](int v) { return graph[v]; }
    std::vector<Edge<Cost>> operator[](int v) const { return graph[v]; }
};

template <class Cost>
std::vector<Cost> dijkstra(const Graph<Cost>& graph, int s) {
    constexpr Cost INF = std::numeric_limits<Cost>::max();

    std::vector<Cost> dist(graph.size(), INF);
    dist[s] = 0;
    MinHeap<std::pair<Cost, int>> que;
    que.emplace(0, s);

    while (!que.empty()) {
        int v;
        Cost d;
        std::tie(d, v) = que.top();
        que.pop();
        if (d > dist[v]) continue;

        for (const auto& e : graph[v]) {
            if (dist[e.dst] <= dist[v] + e.cost) continue;
            dist[e.dst] = dist[v] + e.cost;
            que.emplace(dist[e.dst], e.dst);
        }
    }

    return dist;
}

using ldouble = long double;

void solve() {
    int n, m, s, t;
    std::cin >> n >> m >> s >> t;
    --s, --t;

    std::vector<std::pair<ldouble, ldouble>> ps(n);
    for (auto& p : ps) std::cin >> p.first >> p.second;

    Graph<ldouble> graph(n);
    while (m--) {
        int u, v;
        std::cin >> u >> v;
        --u, --v;

        auto c = std::hypot(ps[u].first - ps[v].first, ps[u].second - ps[v].second);
        graph.span(false, u, v, c);
    }

    auto ds = dijkstra(graph, s);
    std::cout << std::fixed << std::setprecision(10)
              << ds[t] << "\n";
}

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

    solve();

    return 0;
}