import math
r=lambda:list(map(int,input().split()))
N,M=r()
X,Y=r()
p=[r()for _ in range(N)]
P=[r()for _ in range(M)]
l=[[]for _ in range(N)]
for a,b in P:
	l[a-1].append(b-1)
	l[b-1].append(a-1)
q=[X-1]
t=[1e9]*N
t[X-1]=0
while q:
	i=q.pop()
	for j in l[i]:
		a,b=p[i]
		c,d=p[j]
		k=t[i]+math.sqrt((a-c)*(a-c)+(b-d)*(b-d))
		if k<t[j]:
			t[j]=k
			q.append(j)
print(t[Y-1])