n, m = map(int, input().split())
x, y = map(int, input().split())
x, y = x-1, y-1

pq = []
for i in range(n):
    p, q = map(int, input().split())
    pq.append((p, q))

import heapq
INF = 10**18
def dijkstra_heap(s, edge, n):
    d = [INF] * n
    used = [True] * n #True: not used
    d[s] = 0
    used[s] = False
    edgelist = []
    for e in edge[s]:
        heapq.heappush(edgelist,e)
    while len(edgelist):
        minedge = heapq.heappop(edgelist)
        if not used[minedge[1]]:
            continue
        v = minedge[1]
        d[v] = minedge[0]
        used[v] = False
        for e in edge[v]:
            if used[e[1]]:
                heapq.heappush(edgelist,(e[0]+d[v],e[1]))
    return d

edge = [[] for _ in range(n)]
import math
for i in range(m):
    P, Q = map(int, input().split())
    P, Q = P-1, Q-1
    C = math.sqrt((pq[P][0]-pq[Q][0])**2+(pq[P][1]-pq[Q][1])**2)
    edge[P].append((C, Q))
    edge[Q].append((C, P))
d = dijkstra_heap(x, edge, n)
print(d[y])