import sys
input = sys.stdin.readline
import heapq

N,M,S,T=map(int,input().split())
P=[-1]+list(map(int,input().split()))
E=[[] for i in range(N+1)]

for i in range(M):
    a,b=map(int,input().split())
    E[a].append(b)
    E[b].append(a)

X=-P[S]
Q=[(-P[S],S)]
ANS=0
USE=[0]*(N+1)

while Q:
    p,now=heapq.heappop(Q)
    if X<p:
        ANS+=1
        X=p

    for to in E[now]:
        if USE[to]==0:
            USE[to]=1
            heapq.heappush(Q,(-P[to],to))

print(ANS)