import sys
import io, os
input = io.BytesIO(os.read(0,os.fstat(0).st_size)).readline

n, m, s, t = map(int, input().split())
s, t = s-1, t-1
P = list(map(int, input().split()))
g = [[] for i in range(n)]
for i in range(m):
    a, b = map(int, input().split())
    a, b = a-1, b-1
    g[a].append(b)
    g[b].append(a)
x = P[s]
y = 0
q = []
import heapq
q.append((-P[s], s))
heapq.heapify(q)
visit = [False]*n
visit[s] = True
while q:
    p, v = heapq.heappop(q)
    p *= (-1)
    if x > p:
        y += 1
        x = p
    for u in g[v]:
        if visit[u]:
            continue
        visit[u] = True
        heapq.heappush(q, (-P[u], u))
print(y)