from heapq import heapify, heappush as hpush, heappop as hpop
from math import sqrt
import sys
input = lambda: sys.stdin.readline().rstrip()
N, M = map(int, input().split())
s, t = map(int, input().split())
s, t = s-1, t-1

L = []
for _ in range(N):
    a, b = map(int, input().split())
    L.append((a, b))

X = [[] for _ in range(N)]
for _ in range(M):
    a, b = map(int, input().split())
    a, b = a-1, b-1
    d = sqrt((L[a][0] - L[b][0]) ** 2 + (L[a][1] - L[b][1]) ** 2)
    X[a].append([b, d])
    X[b].append([a, d])

def dijkstra(n, E, i0=0):
    h = [[0, i0]]
    D = [-1] * n
    done = [0] * n
    D[i0] = 0
    
    while h:
        d, i = hpop(h)
        done[i] = 1
        for j, w in E[i]:
            nd = d + w
            if D[j] < 0 or D[j] > nd:
                if done[j] == 0:
                    hpush(h, [nd, j])
                    D[j] = nd
    return D

print(dijkstra(N, X, s)[t])