import sys

from heapq import heappush, heappop

input = sys.stdin.buffer.readline

N, M = map(int, input().split())
X, Y = (int(x) - 1 for x in input().split())
INF = 10 ** 10


def dijkstra(N, G, s):
    dist = [INF] * N
    que = [(0, s)]
    dist[s] = 0
    while que:
        c, v = heappop(que)
        if dist[v] < c:
            continue
        for t, cost in G[v]:
            if dist[v] + cost < dist[t]:
                dist[t] = dist[v] + cost
                heappush(que, (dist[t], t))
    return dist


points = [tuple(map(int, input().split())) for _ in range(N)]


def euc_dist(p, q):
    px, py = points[p]
    qx, qy = points[q]
    return ((px - qx) ** 2 + (py - qy) ** 2) ** .5


G = [[] for _ in range(N)]
for _ in range(M):
    p, q = (int(x) - 1 for x in input().split())
    d = euc_dist(p, q)
    G[p].append((q, d))
    G[q].append((p, d))

print(dijkstra(N, G, X)[Y])