def I():return int(input())
def MAP():return map(int,input().split())
def MAPs():return map(str,input().split())
def LI(): return list(map(int,input().split()))
def TPL(): return tuple(map(int,input().split()))
def S():return input()
from collections import defaultdict,Counter,deque
from copy import deepcopy
from heapq import heapify,heappop,heappush
from bisect import bisect_left,bisect_right
from itertools import accumulate,product,permutations,combinations
from math import gcd,ceil,floor,sqrt
inf=float('inf')

n,m=MAP()
start,goal=MAP()
point=[TPL() for _ in range(n)]
g=[[] for _ in range(n)]
for _ in range(m):
    p,q=MAP()
    x,y=point[p-1];X,Y=point[q-1]
    d=(x-X)**2+(y-Y)**2
    d=sqrt(d)
    g[p-1].append((q-1,d))
    g[q-1].append((p-1,d))
def dijkstra(start):
    dst=[10**18]*n
    visit=[False]*n
    q=[]
    heappush(q,(0,start))
    while q:
        now_cost,now_place=heappop(q)
        if visit[now_place]:
            continue
        visit[now_place]=True
        dst[now_place]=now_cost
        for to_place,cost in g[now_place]:
            if visit[to_place]:
                continue
            if dst[to_place]>now_cost+cost:
                dst[to_place]=now_cost+cost
                heappush(q,(dst[to_place],to_place))
    return dst
print(dijkstra(start-1)[goal-1])