import heapq
import math

INF = 1e15

n, m = map(int, input().split())
src, dst = map(int, input().split())
src -= 1
dst -= 1
points = [list(map(int, input().split())) for _ in range(n)]

g = [[] for _ in range(n)]
for _ in range(m):
  u, v = map(int, input().split())
  u -= 1
  v -= 1
  xu, yu = points[u]
  xv, yv = points[v]
  d = math.sqrt((xv - xu) ** 2 + (yv - yu) ** 2)
  g[u].append((v, d))
  g[v].append((u, d))

dist = [INF for _ in range(n)]
dist[src] = 0.0
hp = [(0.0, src)]
while len(hp) > 0:
  cd, cur = heapq.heappop(hp)
  if cd > dist[cur]:
    continue

  for nxt, cost in g[cur]:
    if dist[cur] + cost < dist[nxt]:
      dist[nxt] = dist[cur] + cost
      heapq.heappush(hp, (dist[nxt], nxt))

print(dist[dst])