using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;
using System.Globalization;

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    static int[][] NArr(long n) => Enumerable.Repeat(0, (int)n).Select(_ => NList).ToArray();
    static int[] NMi => ReadLine().Split().Select(c => int.Parse(c) - 1).ToArray();
    static int[][] NMap(int n) => Enumerable.Repeat(0, n).Select(_ => NMi).ToArray();
    static string[] SList(long n) => Enumerable.Repeat(0, (int)n).Select(_ => ReadLine()).ToArray();
    static long[] LList(long n) => Enumerable.Repeat(0, (int)n).Select(_ => long.Parse(ReadLine())).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var c = NList;
        var (n, m) = (c[0], c[1]);
        c = NMi;
        var (x, y) = (c[0], c[1]);
        var map = NArr(n);
        var edges = NMap(m);
        var tree = new List<(int to, double len)>[n];
        for (var i = 0; i < n; ++i) tree[i] = new List<(int to, double len)>();
        foreach (var edge in edges)
        {
            var len = Length(map[edge[0]][0], map[edge[0]][1], map[edge[1]][0], map[edge[1]][1]);
            tree[edge[0]].Add((edge[1], len));
            tree[edge[1]].Add((edge[0], len));
        }
        var llist = Enumerable.Repeat(double.MaxValue / 2, n).ToArray();
        llist[x] = 0;
        var q = new PriorityQueue<(int pos, double len), double>();
        q.Enqueue((x, 0), 0);
        while (q.Count > 0)
        {
            var cur = q.Dequeue();
            if (llist[cur.pos] != cur.len) continue;
            foreach (var next in tree[cur.pos])
            {
                if (llist[next.to] <= cur.len + next.len) continue;
                llist[next.to] = cur.len + next.len;
                q.Enqueue((next.to, llist[next.to]), llist[next.to]);
            }
        }
        WriteLine(llist[y]);
    }
    static double Length(int ax, int ay, int bx, int by)
    {
        return Math.Sqrt(((long)ax - bx) * (ax - bx) + ((long)ay - by) * (ay - by));
    }
}