from heapq import heappop, heappush

N, M = map(int, input().split())
X, Y = map(int, input().split())
pq = [list(map(int, input().split())) for _ in range(N)]
PQ = [list(map(int, input().split())) for _ in range(M)]

G = [[] for _ in range(N)]
for i in range(M):
    a, b = PQ[i]
    a -= 1
    b -= 1
    d = ((pq[a][0]-pq[b][0])**2 + (pq[a][1]-pq[b][1])**2)**0.5
    G[a].append((b, d))
    G[b].append((a, d))

dist = [float('inf')] * N
dist[X-1] = 0

# dijkstra
def dijkstra(s, g):
    que = []
    heappush(que, (0, s))
    while que:
        cost, now = heappop(que)
        if dist[now] < cost:
            continue
        for nxt, d in G[now]:
            if nxt == now:
                continue     
            nxt_cost = dist[now] + d
            if nxt_cost < dist[nxt]:
                dist[nxt] = nxt_cost
                heappush(que, (nxt_cost, nxt))
        
    return dist[g]

ans = dijkstra(X-1, Y-1)
print(ans)