from heapq import heappush, heappop
N, M = map(int, input().split())
X, Y = map(int, input().split())
p = [list(map(int, input().split())) for _ in range(N)]
D = {}
DD = {}
for i in range(M):
    P, Q = map(int, input().split())
    if P-1 in D:
        D[P-1].append(Q-1)
    else:
        D[P-1] = [Q-1]
    if Q-1 in D:
        D[Q-1].append(P-1)
    else:
        D[Q-1] = [P-1]
    DD[(P-1)*N+(Q-1)] = ((p[P-1][0]-p[Q-1][0])**2+(p[P-1][1]-p[Q-1][1])**2) ** 0.5
    DD[(Q-1)*N+(P-1)] = ((p[P-1][0]-p[Q-1][0])**2+(p[P-1][1]-p[Q-1][1])**2) ** 0.5
dist = [int(1e18) for _ in range(N)]
dist[X-1] = 0
pq = []
for i in range(N):
    heappush(pq, [dist[i], i])
while pq != []:
    b = heappop(pq)
    r = b[1]
    if r in D:
        for i in D[r]:
            if dist[i] > dist[r] + DD[r*N+i]:
                dist[i] = dist[r] + DD[r*N+i]
                heappush(pq, [dist[i], i])
print(dist[Y-1])