import sys
input=lambda: sys.stdin.readline().rstrip()
n,m=map(int,input().split())
x,y=map(int,input().split())
PQ=[tuple(int(i) for i in input().split()) for _ in range(n)]

def f(A,B):
  a1,a2=A
  b1,b2=B
  return int((((a1-b1)**2+(a2-b2)**2)**0.5)*10**9)

edge=[[] for i in range(n)]
for _ in range(m):
  p,q=map(int,input().split())
  dis=f(PQ[p-1],PQ[q-1])
  edge[p-1].append(dis*10**6+q-1)
  edge[q-1].append(dis*10**6+p-1)

import heapq
def dijkstra_heap(s):
  d=[float("inf")]*n
  used=[True]*n
  d[s]=0
  used[s]=False
  edgelist=[]
  for e in edge[s]:
    heapq.heappush(edgelist,e)
  while edgelist:
    minedge=heapq.heappop(edgelist)
    minedge_cost=minedge//(10**6)
    minedge_v=minedge%(10**6)
    if not used[minedge_v]:
      continue
    d[minedge_v] = minedge_cost
    used[minedge_v] = False
    for e in edge[minedge_v]:
      e_cost=e//(10**6)
      e_v=e%(10**6)
      if used[e_v]:
        heapq.heappush(edgelist,e+minedge_cost*10**6)
  return d
print(dijkstra_heap(x-1)[y-1]/(10**9))