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
from scipy.sparse import csr_matrix
from scipy.sparse.csgraph import dijkstra

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