import sys
from heapq import heappop, heappush

read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines

N, M = map(int, readline().split())
S, T = map(int, readline().split())
X = [complex(0, 0)] * (N + 1)
for i in range(1, N + 1):
    p, q = map(int, readline().split())
    X[i] = complex(p, q)
G = [[] for _ in range(N + 1)]
m = map(int, read().split())
for p, q in zip(m, m):
    d = abs(X[p] - X[q])
    G[p].append((q, d))
    G[q].append((p, d))

INF = 10.0**18
dist = [INF] * (N+1)
q = [(0, S)]
dist[S] = 0
while q:
    dv, v = heappop(q)
    if dv != dist[v]:
        continue
    for w, d in G[v]:
        dw = dv + d
        if dist[w] > dw:
            dist[w] = dw
            heappush(q, (dw, w))

print(dist[T])