#include <cstdio>
#include <iostream>
#include <string>
#include <sstream>
#include <stack>
#include <algorithm>
#include <cmath>
#include <queue>
#include <map>
#include <set>
#include <cstdlib>
#include <bitset>
#include <tuple>
#include <assert.h>
#include <deque>
#include <bitset>
#include <iomanip>
#include <limits>
#include <chrono>
#include <random>
#include <array>
#include <unordered_map>
#include <functional>
#include <complex>
#include <numeric>
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
constexpr long long MAX = 5100000;
constexpr long long INF = 1LL << 60;
constexpr int inf = 1000000007;
//constexpr long long mod = 1000000007LL;
constexpr long long mod = 998244353LL;
const long double PI = acos((long double)(-1));
using namespace std;
typedef unsigned long long ull;
typedef long long ll;

vector<double> dijkstra(int start, vector<vector<pair<int, double>>>& graph) {
	vector<double> dist(graph.size(), INF); dist[start] = 0;
	priority_queue<pair<double, int>, vector<pair<double, int>>, greater<pair<double, int>>> pq; pq.emplace(0, start);
	while (!pq.empty()) {
		double cost; int idx; tie(cost, idx) = pq.top(); pq.pop();
		if (dist[idx] < cost) continue;
		for (auto next : graph[idx]) if (chmin(dist[next.first], cost + next.second)) pq.emplace(dist[next.first], next.first);
	}
	return dist;
}

using P = pair<int, int>;
double dist(P a, P b) {
	double dx = a.first - b.first;
	double dy = a.second - b.second;
	return sqrt(dx * dx + dy * dy);
}
int main()
{
    /*
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    */
	int n, m; scanf("%d %d", &n, &m);
	int x, y; scanf("%d %d", &x, &y); x--; y--;
	vector<vector<pair<int, double>>> g(n);
	vector<P> vp(n);
	for (int i = 0; i < n; i++) scanf("%d %d", &vp[i].first, &vp[i].second);
	for (int i = 0; i < m; i++) {
		int u, v; scanf("%d %d", &u, &v);
		u--; v--;
		g[u].emplace_back(v, dist(vp[u], vp[v]));
		g[v].emplace_back(u, dist(vp[u], vp[v]));
	}
	auto dist = dijkstra(x, g);
	cout << fixed << setprecision(12) << dist[y] << endl;
    return 0;
}