from collections import defaultdict
from heapq import heappush, heappop
from math import sqrt

N, M = map(int, input().split())
X, Y = map(lambda x: int(x)-1, input().split())

vs = []
for _ in range(N):
    p, q = map(int, input().split())
    vs.append((p, q))

adj = defaultdict(list)
for _ in range(M):
    P, Q = map(lambda x: int(x)-1, input().split())
    adj[P].append(Q)
    adj[Q].append(P)


def dist(a, b) -> float:
    s = vs[a]
    t = vs[b]
    return sqrt((s[0] - t[0]) ** 2 + (s[1] - t[1]) ** 2)


def dijkstrac(start, goal):
    q = [(0.0, start)]
    used = set()
    while q:
        d, v = heappop(q)
        if v == goal: return d
        if v in used: continue
        used.add(v)

        for to in adj[v]:
            if to in used: continue
            heappush(q, (d + dist(v, to), to))

ans = dijkstrac(X, Y)
print(ans)