n,m=map(int,input().split())
S,G=map(int,input().split())
S-=1
G-=1
p=[tuple(map(int,input().split())) for i in range(n)]
e=[[] for i in range(n)]
for i in range(m):
	s,g=map(int,input().split())
	s-=1
	g-=1
	sx,sy=p[s]
	gx,gy=p[g]
	d=((sx-gx)**2+(sy-gy)**2)**0.5
	e[s]+=[(g,d)]
	e[g]+=[(s,d)]
from heapq import heappush,heappop
v=[X]*n
v[S]=0
q=[(v[S],S)]
while len(q)>0:
  sc,sp=heappop(q)
  if sc>v[sp]:
    continue
  for tp,tc in e[sp]:
    if v[tp]>sc+tc:
      v[tp]=sc+tc
      heappush(q,(v[tp],tp))
print(v[G])