from heapq import *

n, m = map(int, input().split())
x, y = map(int, input().split())
x -= 1
y -= 1
point = [list(map(int, input().split())) for _ in range(n)]
edges = [[] for _ in range(n)]
for _ in range(m):
    a, b = map(int, input().split())
    a -= 1
    b -= 1
    edges[a].append(b)
    edges[b].append(a)

def f(i, j):
    dx = point[j][0] - point[i][0]
    dy = point[j][1] - point[i][1]
    return (dx * dx + dy * dy) ** 0.5

inf = 1e20
dist = [inf] * n
dist[x] = 0.0
hq = [(0.0, x)]
while hq:
    d, pos = heappop(hq)
    if dist[pos] < d:
        continue
    for npos in edges[pos]:
        c = f(pos, npos)
        if dist[npos] > d + c:
            dist[npos] = d + c
            heappush(hq, (d + c, npos))
print(dist[y])