from heapq import heappop, heappush
n,m = map(int,input().split())
x,y = map(int,input().split())
x,y = x-1,y-1

PQ = [list(map(int,input().split())) for i in range(n)]
e = [[] for i in range(n)]
for _ in range(m):
    p,q = [int(i)-1 for i in input().split()]
    x1,y1 = PQ[p]
    x2,y2 = PQ[q]
    dis = ((x1-x2)**2+(y1-y2)**2)**0.5
    e[p].append((q,dis))
    e[q].append((p,dis))


inf = 10**10
dis = [inf]*n
dis[x] = 0
h = [[0,x]]
while h:
    d,now = heappop(h)
    if dis[now] != d:
        continue
    for nex,c in e[now]:
        if dis[nex] > d+c:
            dis[nex] = d+c
            heappush(h,[d+c,nex])

print(dis[y])