class UnionFind:
    def __init__(self, n):
        self.n = n
        self.parents = [-1] * n
        self.group = n

    def find(self, x):
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.find(self.parents[x])
            return self.parents[x]

    def union(self, x, y):
        x = self.find(x)
        y = self.find(y)

        if x == y:
            return
        self.group -= 1
        if self.parents[x] > self.parents[y]:
            x, y = y, x

        self.parents[x] += self.parents[y]
        self.parents[y] = x

    def size(self, x):
        return -self.parents[self.find(x)]

    def same(self, x, y):
        return self.find(x) == self.find(y)

    def members(self, x):
        root = self.find(x)
        return [i for i in range(self.n) if self.find(i) == root]

    def roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return self.group

    def all_group_members(self):
        dic = {r:[] for r in self.roots()}
        for i in range(self.n):
            dic[self.find(i)].append(i)
        return dic

    def __str__(self):
        return '\n'.join('{}: {}'.format(r, self.members(r)) for r in self.roots())

n, m, s, t = map(int, input().split())
P = list(map(int, input().split()))
s -= 1
t -= 1
edges = [[] for _ in range(n)]
for _ in range(m):
    a, b = map(int, input().split())
    a -= 1
    b -= 1
    if P[a] > P[b]:
        a, b = b, a
    edges[a].append(b)
    
dic = {}
for i, p in enumerate(P):
    if p not in dic:
        dic[p] = []
    dic[p].append(i)
    
ans = 0
UF = UnionFind(n)
for p in sorted(dic.keys(), reverse = True):
    flg = False
    tmp = []
    for u in dic[p]:
        for v in edges[u]:
            if UF.same(v, s):
                flg = True

    if flg:
        ans += 1
    for u in dic[p]:
        for v in edges[u]:
            UF.union(u, v)
    
print(ans)