#include <iostream>
#include<vector>
#include<algorithm>
#include<string>
#include<map>
#include<set>
#include<stack>
#include<queue>
#include<math.h>
using namespace std;
typedef long long ll;
#define int long long
#define ld long double
typedef vector<ld> VI;
typedef pair<ld, ld> pii;
typedef vector<pii> VP;
typedef vector<string> VS;
typedef priority_queue<int> PQ;
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; }
#define fore(i,a) for(auto &i:a)
#define REP(i,n) for(int i=0;i<n;i++)
#define eREP(i,n) for(int i=0;i<=n;i++)
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define eFOR(i,a,b) for(int i=(a);i<=(b);++i)
#define SORT(c) sort((c).begin(),(c).end())
#define rSORT(c) sort((c).rbegin(),(c).rend())
#define LB(x,a) lower_bound((x).begin(),(x).end(),(a))
#define UB(x,a) upper_bound((x).begin(),(x).end(),(a))
#define INF 1000000000
#define LLINF 922337203685477807
#define mod 1000000007
//priority_queue<int,vector<int>, greater<int> > q2;

int N, M;
int X, Y;
struct edge { 
	int to;
	ld cost;
};

vector<vector<edge> > G;
VI d;

void dikstra(int s) {
	priority_queue<pii, vector<pii>, greater<pii> >que;
	REP(i, N)d[i] = LLINF;
	d[s] = 0;
	que.push(pii(0, s));
	while (!que.empty()) {
		pii p = que.top();
		que.pop();
		int v = p.second;
		if (d[v] < p.first)continue;
		REP(i, G[v].size()) {
			edge e = G[v][i];
			if (d[e.to] > d[v] + e.cost) {
				d[e.to] = d[v] + e.cost;
				que.push(pii(d[e.to], e.to));
			}
		}
	}
}

ld dd(pii a, pii b) {
	return pow((a.first - b.first)*(a.first - b.first) + (a.second - b.second)*(a.second - b.second),0.5);
}

signed main() {
	cin.tie(0);
	ios::sync_with_stdio(false);

	cin >> N >> M;
	G.resize(N);
	d.resize(N);
	cin >> X >> Y;
	X--; Y--;
	VP A(N);
	REP(i, N)cin >> A[i].first >> A[i].second;
	REP(i, M) {
		int u, v; cin >> u >> v; u--; v--;
		ld dis = dd(A[u], A[v]);
		G[u].push_back((edge) { v, dis });
		G[v].push_back((edge) { u, dis });
	}



	dikstra(X);
	printf("%.15Lf\n", d[Y]);
	return 0;
}