import heapq
import math
import sys
input = sys.stdin.buffer.readline
sys.setrecursionlimit(10 ** 7)

N, M = map(int, input().split())
S, T = map(int, input().split())
xy = tuple(tuple(map(int, input().split())) for _ in range(N))
edge = [[] for _ in range(N + 1)]
for _ in range(M):
    p, q = map(int, input().split())
    x1, y1 = xy[p - 1]
    x2, y2 = xy[q - 1]
    d = math.hypot(x1 - x2, y1 - y2)
    edge[p].append((q, d))
    edge[q].append((p, d))

inf = 10**18
dist = [inf] * (N + 1)
dist[S] = 0
que = [(0, S)]
while que:
    c, s = heapq.heappop(que)
    if dist[s] < c:
        continue
    cost = dist[s]
    for t, d in edge[s]:
        if dist[t] > cost + d:
            dist[t] = cost + d
            heapq.heappush(que, (cost+d, t))

print(dist[T])