#include <iostream>
#include <iomanip>
#include <algorithm>
#include <complex>
#include <utility>
#include <vector>
#include <string>
#include <stack>
#include <queue>
#include <tuple>
#include <cmath>
#include <bitset>
#include <cctype>
#include <set>
#include <map>
#include <unordered_map>
#include <numeric>
#include <functional>
#define _overload3(_1,_2,_3,name,...) name
#define _rep(i,n) repi(i,0,n)
#define repi(i,a,b) for(ll i=ll(a);i<ll(b);++i)
#define rep(...) _overload3(__VA_ARGS__,repi,_rep,)(__VA_ARGS__)
#define all(x) (x).begin(),(x).end()
#define PRINT(V) cout << V << "\n"
#define SORT(V) sort((V).begin(),(V).end())
#define RSORT(V) sort((V).rbegin(), (V).rend())
using namespace std;
using ll = long long;
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }
inline void Yes(bool condition){ if(condition) PRINT("Yes"); else PRINT("No"); }
template<class itr> void cins(itr first,itr last){
    for (auto i = first;i != last;i++){
        cin >> (*i);
    }
}
template<class itr> void array_output(itr start,itr goal){
    string ans = "",k = " ";
    for (auto i = start;i != goal;i++) ans += to_string(*i)+k;
    if (!ans.empty()) ans.pop_back();
    PRINT(ans);
}
ll gcd(ll a, ll b) {
    return a ? gcd(b%a,a) : b;
}
const ll INF = 1e18;
const ll MOD = 1000000007;
const ll MOD2 = 998244353;
typedef pair<ll,ll> P;
typedef pair<double,double> point;
const ll MAX = 200000;
constexpr ll nx[8] = {1,0,-1,0,1,-1,1,-1};
constexpr ll ny[8] = {0,1,0,-1,1,1,-1,-1};
class Dijkstra{
    private:
        struct edge{
            int to;
            double cost;
        };
        vector<vector<edge>> G;
        vector<double> d;
        int siz;
    public:
        Dijkstra(int n){
            G.resize(n);
            siz = n;
        }
        void add_edge(int from,int to,double cost){
            G[from].push_back(edge{to,cost});
        }
        vector<double> dijkstra(int s){
            priority_queue<P,vector<P>,greater<P>> q;
            d.assign(siz,1e9);
            d[s] = 0.0;
            q.push(P(0,s));
            while(!q.empty()){
                P p = q.top();q.pop();
                int v = p.second;
                if (d[v] < p.first) continue;
                for(edge &e:G[v]){
                    if (chmin(d[e.to],d[v]+e.cost)){
                        q.push(P(d[e.to],e.to));
                    }
                }
            }
            return d;
        }
};
double dis(double x1,double y1,double x2,double y2){
    return sqrt(pow(x1-x2,2)+pow(y1-y2,2));
}
int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    ll n,m,x,y;
    cin >> n >> m >> x >> y;
    x--;
    y--;
    vector<vector<double>> cost(n,vector<double>(2));
    rep(i,n){
        cin >> cost[i][0] >> cost[i][1];
    }
    Dijkstra g(n);
    ll p,q;
    rep(i,m){
        cin >> p >> q;
        p--;
        q--;
        g.add_edge(p,q,dis(cost[p][0],cost[p][1],cost[q][0],cost[q][1]));
        g.add_edge(q,p,dis(cost[p][0],cost[p][1],cost[q][0],cost[q][1]));
    }
    vector<double> d = g.dijkstra(x);
    printf("%.10f\n",d[y]);
}