## https://yukicoder.me/problems/no/1065

import heapq
import math



def main():
    N, M = map(int, input().split())
    X, Y = map(int, input().split())
    X -= 1
    Y -= 1
    pq = []
    for _ in range(N):
        p, q = map(int, input().split())
        pq.append((p, q))
    
    next_nodes = [[] for _ in range(N)]
    for _ in range(M):
        P, Q = map(int, input().split())
        P -= 1
        Q -= 1

        p0, q0 = pq[P]
        p1, q1 = pq[Q]
        d = math.sqrt((p0 - p1) ** 2 + (q0 - q1) ** 2)
        next_nodes[P].append((Q, d))
        next_nodes[Q].append((P, d))
    
    seen = [float("inf") for _ in range(N)]
    fix = [float("inf") for _ in range(N)]
    seen[X] = 0.0
    queue = []
    heapq.heappush(queue, (0.0, X))
    while len(queue) > 0:
        cost, v = heapq.heappop(queue)
        if fix[v] < float("inf"):
            continue

        fix[v] = cost
        for w, d in next_nodes[v]:
            if fix[w] < float("inf"):
                continue

            new_cost = d + cost
            if seen[w] > new_cost:
                seen[w] = new_cost
                heapq.heappush(queue, (new_cost, w))
    print(fix[Y])









if __name__ == '__main__':
    main()