from heapq import heappush, heappop
INF = 10 ** 9
def dijkstra(s, n): # (始点, ノード数)
    dist = [INF] * n
    hq = [(0, s)] # (distance, node)
    dist[s] = 0
    seen = [False] * n # ノードが確定済みかどうか
    while hq:
        tmp = heappop(hq) # ノードを pop する
        v = tmp[1]
        c = tmp[0]
        seen[v] = True
        if dist[v] != c:
            continue
        for to, cost in adj[v]: # ノード v に隣接しているノードに対して
            if seen[to] == False and dist[v] + cost < dist[to]:
                dist[to] = dist[v] + cost
                heappush(hq, (dist[to], to))
    return dist

n,m = map(int,input().split())
x,y = map(int,input().split())
pq = [[int(i) for i in input().split()] for j in range(n)]
PQ = [[int(i) for i in input().split()] for j in range(m)]

adj = [[] for i in range(n)]

for i in range(m):
    P,Q = PQ[i]
    P -= 1
    Q -= 1
    lp = pq[P]
    lq = pq[Q]
    tmp = ((lp[0]-lq[0])**2+(lp[1]-lq[1])**2)**0.5
    adj[P].append([Q,tmp])
    adj[Q].append([P,tmp])

x -= 1
y -= 1
di = dijkstra(x,n)
print(di[y])