#!/usr/bin/env pypy3

import heapq
import math
 
 
INF = 10 ** 8


def dijkstra(num_vertices, adj_list, source=0):
    dist = [INF for _ in range(num_vertices)]
    dist[source] = 0
    pq = [(dist[u], u) for u in range(num_vertices)]
    heapq.heapify(pq)
    while pq:
        _, u = heapq.heappop(pq)
        for v, cost in adj_list[u]:
            new_length = dist[u] + cost
            if new_length < dist[v]:
                dist[v] = new_length
                heapq.heappush(pq, (new_length, v))
    return dist



def minimize(n, adj_list, pole_start, pole_end):
    dist = dijkstra(n, adj_list, pole_start)
    res = dist[pole_end]
    return res


def main():
    n, m = (int(z) for z in input().split())
    pole_start, pole_end = (int(z) - 1 for z in input().split())
    pole_poss = []
    for _ in range(n):
        x0, y0 = (float(z) for z in input().split())
        pole_poss.append((x0, y0))
    adj_list = [set() for _ in range(n)]
    for _ in range(m):
        st, en = (int(z) - 1 for z in input().split())
        dist = math.hypot(pole_poss[st][0] - pole_poss[en][0], pole_poss[st][1] - pole_poss[en][1])
        adj_list[st].add((en, dist))
        adj_list[en].add((st, dist))
    res = minimize(n, adj_list, pole_start, pole_end)
    print("{:.8f}".format(res))


if __name__ == '__main__':
    main()