import times, strutils, sequtils, math, algorithm, tables, sets, lists, intsets
import critbits, future, strformat, deques,heapqueue
template `max=`(x,y) = x = max(x,y)
template `min=`(x,y) = x = min(x,y)
template `mod=`(x,y) = x = x mod y
template scan2 = (scan(), scan())
template scan3 = (scan(), scan())
let read* = iterator: string {.closure.} =
    while true: (for s in stdin.readLine.split: yield s)
proc scan(): int = read().parseInt
proc scanf(): float = read().parseFloat
proc toInt(c:char): int =
    return int(c) - int('0')



proc solve():float=
  var
    n = scan()
    m = scan()
    x = scan()-1
    y = scan()-1
    pole = newseqwith(n,(scanf(),scanf()))
    es = newseqwith(n,newseq[int]())
    cs = newseqwith(n,newseq[int]())

  for i in 0..<m:
    var
      p = scan()-1
      q = scan()-1
      dist = (sqrt((pole[p][0]-pole[q][0])^2+(pole[p][1]-pole[q][1])^2)*1E8).toInt()
    es[p].add(q)
    cs[p].add(dist)
    es[q].add(p)
    cs[q].add(dist)

  var
    dist = newseqwith(n,int.high.div(4))
  proc dijkstra(s:int)=
    dist[s]=0
    var
      q = initHeapQueue[(int,int)]()
    q.push((0,s))
    while q.len>0:
      var
        (c,p) = q.pop()

      if dist[p]<c:continue
      else:
        for ni in 0..<es[p].len:
          var
            nxt = es[p][ni]
            cst = cs[p][ni]
          if dist[p]+cst < dist[nxt]:
            dist[nxt]=dist[p]+cst
            q.push((dist[nxt],nxt))
  dijkstra(x)
  return dist[y].float/1E8


    


  
echo solve()