import heapq
n, m = map(int, input().split())
x, y = map(int, input().split())
pq = []
for _ in range(n):
    p, q = map(int, input().split())
    pq.append((p, q))
graph = [[] for _ in range(n)]
for _ in range(m):
    u, v = map(int, input().split())
    graph[u-1].append(v-1)
    graph[v-1].append(u-1)
f = lambda a, b: ((a[0]-b[0])**2+(a[1]-b[1])**2)**0.5
INF = 10**9
heap = []
dist = [INF]*n
dist[x-1] = 0
heap = [(0, x-1)]
heapq.heapify(heap)
while heap:
    _, node = heapq.heappop(heap)
    for i in graph[node]:
        if dist[i] > dist[node] + f(pq[node], pq[i]):
            dist[i] = dist[node] + f(pq[node], pq[i])
            heapq.heappush(heap, (dist[i], i))
print(dist[y-1])