#pragma GCC target("avx2")
#pragma GCC optimize("03")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>
using namespace std; typedef long double ld; typedef long long ll;
typedef unsigned long long ull;
#define endl "\n"
#define FOR(i,a,b) for(int i=(a);i<=(b);i++)
#define rep(i,n) for(int i=0;i<(n);i++)
#define PII pair<int, int>
#define PLL pair<ll, ll>
#define ALL(x) (x).begin(), (x).end()
int dx[] = {1, 0, -1, 0}; int dy[] = {0, 1, 0, -1};
constexpr int INF=1<<30;
constexpr ll LINF=1LL<<60; 
constexpr ll mod=1e9+7;
template<class T>vector<T> vec(int len, T elem) { return vector<T>(len, elem); } // auto dp = vec(52, vec(103, vec(103, INF)));
template<class T>inline bool chmax(T &a, const T &b) { if (a<b) { a = b; return 1; } return 0; }
template<class T>inline bool chmin(T &a, const T &b) { if (b<a) { a = b; return 1; } return 0; }
template<class T>inline int popcount(T a) {return __builtin_popcount(a);}
template<class T>inline T emod(T a, T p) { return (a%p + p) % p;}
template <typename T> istream &operator>>(istream &is, vector<T> &vec) { for (auto &v : vec) is >> v; return is; }
template <typename T> ostream &operator<<(ostream &os, const vector<T> &vec) {os << '\n'; for (auto v : vec) os << v << ' '; os << '\n'; return os;}
template <typename T> ostream &operator<<(ostream &os, const deque<T> &vec) { os << "deq["; for (auto v : vec) os << v << ','; os << ']'; return os; }
template <typename T> ostream &operator<<(ostream &os, const set<T> &vec) { os << '{'; for (auto v : vec) os << v << ','; os << '}'; return os; }
template <typename T> ostream &operator<<(ostream &os, const unordered_set<T> &vec) { os << '{'; for (auto v : vec) os << v << ','; os << '}'; return os; }
template <typename T> ostream &operator<<(ostream &os, const multiset<T> &vec) { os << '{'; for (auto v : vec) os << v << ','; os << '}'; return os; }
template <typename T> ostream &operator<<(ostream &os, const unordered_multiset<T> &vec) { os << '{'; for (auto v : vec) os << v << ','; os << '}'; return os; }
template <typename T1, typename T2> ostream &operator<<(ostream &os, const pair<T1, T2> &pa) { os << '(' << pa.first << ',' << pa.second << ')'; return os; }
template <typename TK, typename TV> ostream &operator<<(ostream &os, const map<TK, TV> &mp) { os << '{'; for (auto v : mp) os << v.first << "=>" << v.second << ','; os << '}'; return os; }
template <typename TK, typename TV> ostream &operator<<(ostream &os, const unordered_map<TK, TV> &mp) { os << '{'; for (auto v : mp) os << v.first << "=>" << v.second << ','; os << '}'; return os; }
struct MyIO {
    MyIO(){
        cin.tie(0); 
        ios::sync_with_stdio(false); 
        cout << fixed << setprecision(15);
    }
} IO_OI;
#ifdef LOCAL
void debug_out() { cerr << endl; }
template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
    cerr << " " << H;
    debug_out(T...);
}
#define debug(...) \
    cerr << __LINE__ << " [" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#define dump(x) cerr << __LINE__ << " " << #x << " = " << (x) << endl
#else
#define debug(...) (void(0))
#define dump(x) (void(0))
#endif
//-------------------
template<class T>
struct Dijkstra {
    using PEC = pair<T, int>;
    struct Edge {
        int to;
        T cost;
        Edge(int to, T cost):to(to),cost(cost) {}
    };
    vector<vector<Edge>> G;
    vector<T> d;
    int N;
    T MXX;
    Dijkstra(int n, T mx): N(n), MXX(mx) {
        d.assign(N, MXX);
        G.assign(N, vector<Edge>());
    }
    void add_edge(int from, int to, T cost) {
        G[from].emplace_back(to, cost);
    }
    vector<T> build(int s) {
        priority_queue<PEC, vector<PEC>, greater<PEC> > que;
        que.push({0, s});

        while (!que.empty()) {
            PEC p = que.top();
            que.pop();
            int v = p.second;
            if (d[v] <= p.first) continue;
            d[v] = p.first;
            for (auto e: G[v]) {
                if (d[e.to] > d[v] + e.cost) { // make code faster
                    que.push({d[v] + e.cost, e.to});
                }
            }
        }
        return d;
    } 
};

int main(){
    int n,m;cin>>n>>m;
    int x,y;cin>>x>>y;x--;y--;
    vector<ld> X(n);
    vector<ld> Y(n);
    rep(i,n) cin>>X[i]>>Y[i];
    Dijkstra dj(n, (ld) 1e15);
    auto dist = [&](int pp, int qq)-> ld {
        return sqrt((X[pp]-X[qq])*(X[pp]-X[qq])+(Y[pp]-Y[qq])*(Y[pp]-Y[qq]));
    };
    rep(i,m) {
        int p,q;cin>>p>>q;p--;q--;
        dj.add_edge(p, q, dist(p,q));
        dj.add_edge(q, p, dist(p,q));
    }

    dj.build(x);
    debug(dj.d);

    cout << dj.d[y] << endl;
    return 0;
}