import heapq
import sys
input = sys.stdin.buffer.readline
sys.setrecursionlimit(10 ** 7)

N, M, S, T = map(int, input().split())
P = tuple(map(int, input().split()))
S -= 1
T -= 1
G = [[] for _ in range(N)]
for _ in range(M):
    a, b = map(int, input().split())
    a -= 1
    b -= 1
    G[a].append(b)
    G[b].append(a)

seen = [0] * N
seen[S] = 1
q = [(-P[S], S)]
X = P[S]
Y = 0
while q:
    p, s = heapq.heappop(q)
    p = -p
    if p < X:
        X = p
        Y += 1
    for t in G[s]:
        if seen[t]:
            continue
        heapq.heappush(q, (-P[t], t))
        seen[t] = 1

print(Y)