import sys
input = sys.stdin.readline
from heapq import *

def dijkstra():
    dist = [10**18]*N
    dist[X-1] = 0
    pq = []
    heappush(pq, (dist[X-1], X-1))
    
    while pq:
        d, v = heappop(pq)
        
        if dist[v]<d:
            continue
        
        for nv, w in G[v]:
            if dist[nv]>dist[v]+w:
                dist[nv] = dist[v]+w
                heappush(pq, (dist[nv], nv))
    
    return dist

N, M = map(int, input().split())
X, Y = map(int, input().split())
pq = [tuple(map(int, input().split())) for _ in range(N)]
G = [[] for _ in range(N)]

for _ in range(M):
    s, t = map(int, input().split())
    ps, qs = pq[s-1]
    pt, qt = pq[t-1]
    d = ((ps-pt)**2+(qs-qt)**2)**0.5
    G[s-1].append((t-1, d))
    G[t-1].append((s-1, d))

print(dijkstra()[Y-1])