#include <bits/stdc++.h>
#define all(vec) vec.begin(), vec.end()
#define pb push_back
#define eb emplace_back
#define fi first
#define se second
using namespace std;
using ll = long long;
using P = pair<ll, ll>;
template <class T>
using V = vector<T>;
template <class T>
inline void chmin(T &a, const T &b) { a = min(a, b); }
template <class T>
inline void chmax(T &a, const T &b) { a = max(a, b); }
template <class T>
inline bool kbit(const T &x, const int &k) { return ((x >> k) & 1LL); }
inline int popcount(const int &n) { return __builtin_popcount(n); }
inline ll popcountll(const ll &n) { return __builtin_popcountll(n); }
template <class T>
void zip(V<T> &v) {
    sort(all(v));
    v.erase(unique(all(v)), v.end());
}
void dump() {
    cerr << '\n';
}
template <class Head, class... Tail>
void dump(Head &&head, Tail &&... tail) {
    cerr << head << (sizeof...(Tail) == 0 ? " " : ", ");
    dump(std::move(tail)...);
}
template <class T>
void print(const vector<T> &v) {
    for (int i = 0; i < v.size(); i++) cout << v[i] << (i + 1 == v.size() ? '\n' : ' ');
}
template <class T>
void read(vector<T> &v) {
    for (int i = 0; i < v.size(); i++) cin >> v[i];
}
constexpr char sp = ' ', newl = '\n';
constexpr int dx[4] = {0, 1, 0, -1}, dy[4] = {1, 0, -1, 0};
constexpr ll INF = (1LL << 30) - 1LL;
constexpr ll MOD = 1e9 + 7;
//@docs Docs/Dijkstra.md
template <class T>
struct Dijkstra {
    int n;
    vector<vector<pair<int, T>>> G;
    Dijkstra(int n) : n(n), G(n) {}
    void addedge(const int &u, const int &v, const T &c) { G[u].emplace_back(v, c); }
    vector<T> dijkstra(const int &st) {
        priority_queue<pair<T, int>, vector<pair<T, int>>, greater<pair<T, int>>> q;
        vector<T> d(n, INF);
        d[st] = 0;
        q.emplace(0, st);
        while (!q.empty()) {
            int v = q.top().second;
            T dd = q.top().first;
            q.pop();
            if (d[v] < dd) continue;
            for (auto &e : G[v]) {
                if (d[e.first] > d[v] + e.second) {
                    d[e.first] = d[v] + e.second;
                    q.emplace(d[e.first], e.first);
                }
            }
        }
        return d;
    }
};
int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    int n, m;
    cin >> n >> m;
    int a, b;
    cin >> a >> b;
    --a;
    --b;
    V<double> x(n), y(n);
    for (int i = 0; i < n; i++) {
        cin >> x[i] >> y[i];
    }
    Dijkstra<double> g(n);
    for (int i = 0; i < m; i++) {
        int u, v;
        cin >> u >> v;
        --u;
        --v;
        double d = sqrt(pow(x[u] - x[v], 2) + pow(y[u] - y[v], 2));
        g.addedge(u, v, d);
        g.addedge(v, u, d);
    }
    cout << fixed << setprecision(15) << g.dijkstra(a)[b] << newl;
}