import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines
sys.setrecursionlimit(10 ** 7)

from math import sqrt


def dijkstra_heap(s):
    import heapq
    # 始点sから各頂点への最短距離
    d = [float("inf")] * n
    used = [True] * n  # True:未確定
    d[s] = 0
    used[s] = False
    edgelist = []
    for e in graph[s]:
        e.append(s)
        heapq.heappush(edgelist, e)
    while len(edgelist):
        minedge = heapq.heappop(edgelist)
        # まだ使われてない頂点の中から最小の距離のものを探す
        if not used[minedge[1]]:
            continue
        v = minedge[1]
        d[v] = minedge[0]
        used[v] = False
        for e in graph[v]:
            if used[e[1]]:
                heapq.heappush(edgelist, [e[0] + d[v], e[1]])
    return d


n, m = map(int, readline().split())
x, y = map(int, readline().split())
pq = [list(map(int, readline().split())) for _ in range(n)]
graph = [[] for _ in range(n)]
for i in range(m):
    p, q = map(int, readline().split())
    p -= 1
    q -= 1
    v = sqrt((pq[p][0] - pq[q][0]) ** 2 + (pq[p][1] - pq[q][1]) ** 2)
    graph[p].append([v, q])
    graph[q].append([v, p])
print(dijkstra_heap(x - 1)[y - 1])