N,M=map(int,input().split())
X,Y=map(int,input().split())
L=[tuple(map(int,input().split())) for i in range(N)]
E=[[] for i in range(N+1)]

from math import sqrt

for i in range(M):
    p,q=map(int,input().split())
    p-=1
    q-=1
    x0,y0=L[p]
    x1,y1=L[q]
    E[p].append((sqrt((x0-x1)**2+(y0-y1)**2),q))
    E[q].append((sqrt((x0-x1)**2+(y0-y1)**2),p))

import heapq
DP=[1<<62]*(N+1)
DP[X-1]=0

Q=[(0,X-1)]

while Q:
    now,x=heapq.heappop(Q)

    for le,to in E[x]:
        if DP[to]>DP[x]+le:
            DP[to]=DP[x]+le
            heapq.heappush(Q,(DP[to]+le,to))
print(DP[Y-1])