import java.util.*;
import java.io.*;

public class Main {
    public static void main(String[] args) throws Exception{
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        String[] first = br.readLine().split(" ", 2);
        int n = Integer.parseInt(first[0]);
        int m = Integer.parseInt(first[1]);
        String[] second = br.readLine().split(" ", 2);
        int x = Integer.parseInt(second[0]) - 1;
        int y = Integer.parseInt(second[1]) - 1;
        ArrayList<ArrayList<Integer>> graph = new ArrayList<>();
        Node[] nodes = new Node[n];
        for (int i = 0; i < n; i++) {
            String[] line = br.readLine().split(" ", 2);
            nodes[i] = new Node(i, Integer.parseInt(line[0]), Integer.parseInt(line[1]));
            graph.add(new ArrayList<>());
        }
        for (int i = 0; i < m; i++) {
            String[] line = br.readLine().split(" ", 2);
            int a = Integer.parseInt(line[0]) - 1;
            int b = Integer.parseInt(line[1]) - 1;
            graph.get(a).add(b);
            graph.get(b).add(a);
        }
        double[] costs = new double[n];
        Arrays.fill(costs, Double.MAX_VALUE);
        PriorityQueue<Path> queue = new PriorityQueue<>();
        queue.add(new Path(x, 0));
        while (queue.size() > 0) {
            Path p = queue.poll();
            if (costs[p.idx] <= p.value) {
                continue;
            }
            costs[p.idx] = p.value;
            for (int next : graph.get(p.idx)) {
                queue.add(new Path(next, p.value + nodes[next].getDistance(nodes[p.idx])));
            }
        }
        System.out.println(costs[y]);
    }
    

    static class Path implements Comparable<Path> {
        int idx;
        double value;

        public Path(int idx, double value) {
            this.idx = idx;
            this.value = value;
        }
        
        public int compareTo(Path another) {
            if (value == another.value) {
                return 0;
            } else if (value < another.value) {
                return -1;
            } else {
                return 1;
            }
        }
    }
    
    static class Node {
        int idx;
        int x;
        int y;
        
        public Node(int idx, int x, int y) {
            this.idx = idx;
            this.x = x;
            this.y = y;
        }
        
        public double getDistance(Node another) {
            return Math.sqrt(Math.pow(x - another.x, 2) + Math.pow(y - another.y, 2));
        }
        
        public int hashCode() {
            return idx;
        }
        
        public boolean equals(Object o) {
            Node n = (Node)o;
            return idx == n.idx;
        }
    }
}