import sys

sys.setrecursionlimit(200005)
int1 = lambda x: int(x)-1
p2D = lambda x: print(*x, sep="\n")
def II(): return int(sys.stdin.buffer.readline())
def LI(): return list(map(int, sys.stdin.buffer.readline().split()))
def LI1(): return list(map(int1, sys.stdin.buffer.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def LLI1(rows_number): return [LI1() for _ in range(rows_number)]
def BI(): return sys.stdin.buffer.readline().rstrip()
def SI(): return sys.stdin.buffer.readline().rstrip().decode()
# dij = [(0, 1), (-1, 0), (0, -1), (1, 0)]
# dij = [(0, 1), (-1, 0), (0, -1), (1, 0), (1, 1), (1, -1), (-1, 1), (-1, -1)]
dij = [(0, 1), (1, 0), (1, 1), (1, -1)]
inf = 10**16
# md = 998244353
md = 10**9+7

from heapq import *

def Dist(u, v):
    x0, y0 = xy[u]
    x1, y1 = xy[v]
    return ((x1-x0)**2+(y1-y0)**2)**0.5

n, m = LI()
su, gu = LI1()
xy = LLI(n)
to = [[] for _ in range(n)]
for _ in range(m):
    u, v = LI1()
    d = Dist(u, v)
    to[u].append((v, d))
    to[v].append((u, d))

dist = [inf]*n
dist[su] = 0
hp = [(0, su)]
while hp:
    d, u = heappop(hp)
    if u == gu:
        print(d)
        break
    if d > dist[u]: continue
    for v, c in to[u]:
        nd = d+c
        if nd >= dist[v]: continue
        dist[v] = nd
        heappush(hp, (nd, v))