from heapq import heappush, heappop, heapify
import sys
input = sys.stdin.readline

def main():
    N, M = list(map(int, input().split()))
    X, Y = list(map(int, input().split()))
    X -= 1; Y -= 1
    pq = [list(map(int, input().split())) for i in range(N)]
    g = [[] for i in range(N)]
    INF = float('inf')
    dist = [INF for i in range(N)]
    visited = [False] * N

    for i in range(M):
        p, q = list(map(int, input().split()))
        p -= 1; q -= 1

        px, py = pq[p]
        qx, qy = pq[q]

        d = ((px-qx)**2 + (py-qy)**2) **0.5
        g[p].append((d, q))
        g[q].append((d, p))

    q = g[X]
    heapify(q)
    dist[X] = 0
    visited[X] = True

    while q:
        c, v = heappop(q)

        if visited[v]: continue
        visited[v] = True
        dist[v] = c
        if v == Y:
            print(c)
            break

        for d, u in g[v]:
            if not visited[u]: heappush(q, (c+d, u))

if __name__ == '__main__':
    main()