#yuki1065
from collections import deque
from math import sqrt

N,M=map(int,input().split())
X,Y=map(int,input().split())
X-=1
Y-=1
pq=[list(map(int,input().split())) for i in range(N)]
PQ=[list(map(int,input().split())) for i in range(M)]
edge=[[] for i in range(N)]
for P,Q in PQ:
 edge[P-1].append(Q-1)
 edge[Q-1].append(P-1)

q=deque([X])
res=[float('inf')]*N
res[X]=0
while q:
 i=q.popleft()
 for j in edge[i]:
  a,b=pq[i]
  c,d=pq[j]
  k=res[i]+sqrt((a-c)**2+(b-d)**2)
  if k<res[j]:
   res[j]=k
   q.append(j)
print(res[Y])